While I am sure that there are many plays that could use improvement, I tried to find where the game was lost. I think that the game was close at around move 100, but White quickly took the lead. Go to move 101.
(;FF[4]ST[2]GM[1]SZ[19]CA[UTF-8]AP[GOWrite:2.3.46]RE[W+25.5]FG[259:]PM[2]GN[ ]PB[Me]PW[GNU Go, Level 10]PC[Home]DT[13-06-2016]RU[Japanese]
;B[qd]
;W[pp]
;B[dq]
;W[dd]
;B[fc]
;W[do]
(
;B[dk]TR[oc][qn][nq]SQ[dk]L[co]C[Considered playing at the triangled points.
Chose for D9, intending to continue at A with the normal variation if white would play away. Then the D5 group would be left in a pincer.]
(
;W[cq]
;B[dp]
;W[cp]
;B[gp]
;W[oc]
(
;B[qg]
;W[fd]
(
;B[gc]
;W[ec]
;B[gd]
;W[lc]
;B[jc]C[A simple variation, but I feel that this is OK. White does have a big top left corner though.]
;W[iq]
;B[cf]C[Approach; if white answers at B16, I'll play C11, and try to get the entire left side.]
;W[fe]
;B[bd]
;W[ge]
;B[he]
;W[lq]
;B[dh]
;W[gh]
;B[cm]
;W[cn]
;B[dm]C[Black now has the entire left side, as planned, but white has the bottom as potential territory.]
;W[qb]
;B[rc]
;W[ql]C[I feel that this is greedy. Somehow this should be punished, but I don't know how, apart from directly jumping into the 3-3 point.]
;B[qq]
;W[pq]
;B[qp]
;W[qo]
;B[ro]
;W[qn]
;B[rn]
;W[qi]
;B[pr]
;W[or]
;B[qr]
;MA[cg][ga][ha][ia][sq][so][ak][rq][bk][ck][ae][be][ss][cl][bl][rd][qs][sd][rs][al][ai][hc][bi][ic][ci][af][id][sr][bf][hd][rr][rp][sp][hb][ah][ib][ch][gb][bh][rf][sf][cj][bj][aj][re][bg][se][ag]TR[jp][ph][pj][hg]SQ[rk][sk][ma][na][oa][pa][bo][ao][ks][jr][ls][kr][ms][co][ns][js][mr][rj][lr][sj][nr][pb][ob][nb][mb][bq][bp][aq][ap]C[This is a standard joseki, and black takes another corner. Lets count some (potential) points:
X Black 48
O White 29
I feel black is ahead by a cofortable lead, but the dreaded huge middle is already beginning to form. If I can prevent white from making a huge territory in the middle, and not invade my own, I should be winning.
I'm thinking about the triangled squares to get influence towards the middle.]W[nq]
;B[hg]
;W[ep]C[White ignores the hit at H13. Could I cut off the entire top left group in exchange for the three bottom left stones?]
(
;B[eq]C[Possibly not; can't read this out for sure. First try to save the bottom left group.]
;W[fp]
;B[fq]
;TR[jg][oh][ph]W[rm]C[Don't need to react to this yet.
Thinking about the triangled squares to get ingo the middle. I think I can save the lower left group if cut at G3, by playing G2.]
;B[jg]C[Getting into the middle, and also trying to build some more territory at the top.]
;TR[kd]W[fm]C[I'm going to try and lean on the M17 stone to expand the the territory at the top, and get more influence towards the center.]
;B[kd]
;W[ho]C[Ignored. Let's try and settle this group once and forever.]
;B[hq]
;W[dr]
;B[er]
;W[cr]
;B[ir]
;W[go]
;B[jq]
;W[ip]
;B[gr]
;W[jp]C[It should be alive now. But I'm not 100% sure... need more life & death training apparently.]
;B[kr]
;TR[lf][og]W[oe]C[White is also starting towards the center. I'm thinking about P13, but I'm afraid that he will try to invade using an attachment at R15 or somethig like that, and cut off P13 and R13.
I'm also thinking to just enlarge the top territory some more with M14, and get another stone towards the center.]
;B[qe]
;W[ji]C[Craptastic. A cap and a large knight. I feel this should never work, but most of the time it does.]
;B[lh]
;MA[ke][ie][ga][je][ha][ia][sq][ja][rq][ae][be][cl][bl][al][ai][bi][ci][if][jf][id][sr][kf][hd][rr][rp][jd][sp][rf][sf][cj][bj][aj][re][gq][se][cg][ak][so][bk][ck][rg][ss][sg][qs][rd][rs][sd][jr][hr][fr][hc][hs][ic][is][js][fs][af][bf][jb][hb][ah][ib][ch][gb][bh][bg][ag]TR[pj][fj][nj][oj][fk]SQ[jm][im][lm][km][ii][hm][gm][nm][ma][mm][na][pm][oa][om][pa][gl][il][hl][gi][hi][rj][sj][kp][lp][mp][rl][sl][pl][jj][kj][nl][hj][ol][ij][ll][np][ml][gj][op][jl][kl][mo][gk][no][hk][ik][ko][lo][jk][kk][lk][mk][oo][nk][po][ok][pk][rk][sk][jo][io][pn][hn][in][jn][pb][kn][ln][ob][mn][nb][nn][mb][on][gn]C[Let's count some points again...
X Black: 67 points
O White: 76 points
If white gets the entire middle, I'll lose the game. Somehow, I must invade now, at the open triangled spaces.]W[lj]
;B[fj]
;W[gk]
;B[gj]
;W[hk]
;B[ij]
;W[jl]C[White's top left group is getting into danger while he's defending the middle.]
;B[jj]
;W[df]C[Defending the top left group. I so want to connect at G10, and the further invade through L9, but I feel I have to first fix the left side.]
;B[cg]
;W[hj]C[Thought so.]
;B[ii]
;W[eh]
;B[di]C[Again, I feel I have to first fix the left side.]
;W[ce]
;B[be]
;W[rb]C[I think this is a mistake.]
;B[kk]
(
;MA[ke][ie][ga][je][ha][sq][ia][ja][rq][ae][cl][bl][al][ai][bi][ci][if][jf][id][sr][kf][hd][rr][rp][jd][sp][rf][sf][cj][bj][aj][re][se][gq][ad][kg][ak][so][bk][ck][ss][rd][qs][sd][rs][jr][hr][gs][fr][hc][hs][is][ic][js][fs][af][bf][jb][ah][hb][ib][ch][bh][gb][bg][ag]SQ[jm][im][lm][ee][km][hm][gm][nm][ma][mm][na][de][pm][oa][om][pa][gl][qa][il][hl][rj][kp][sj][lp][ed][mp][rl][sl][np][op][oq][bq][aq][bp][ap][eg][no][fg][ko][lo][oo][po][rk][sk][br][ar][bo][ao][co][jo][io][ef][ff][cs][bs][as][pn][hn][in][jn][pb][kn][ln][ob][mn][nb][mb][on][gn]C[White is backing off. The reduction seems to be working. Let's count some points again:
X Black: 66
O White: 69
Black is still behind, but the gap is closing. This could be a very close game.]W[ml]
;B[kl]
;W[en]C[White is playing away. I do not understand why.]
;B[kn]
;W[lo]
;B[ln]
;W[mn]
;B[ni]
;W[nj]
;B[oi]C[Territory reduction still going strong. I don't want to take any risk.]
;W[oj]
(
;B[jm]C[*** Not very large. See variations.]
;W[eb]
;B[fb]C[*** Takes gote. Not as big as other plays.]
;W[kb]C[White is beginning the endgame.]
;B[jb]C[*** Takes gote. Not so big.]
;W[rh]
;B[rg]C[*** Takes gote. Maybe necessary.]
;W[me]C[*** Big. Maybe now White has a won game, assuming best play.
]
;B[lf]C[*** Gote. Small.]
;W[bn]C[*** How can Black catch up now?
Go to move 125.]
;B[bm]
;W[am]
;B[al]
;W[an]
;B[bl]C[As soon as I get sente again, I can try and reduce the middle further.]
;W[mi]
;B[mh]
;W[sn]
;B[sp]
;TR[in][im][cb][cc][ko][ea][ka][qh]W[il]C[I feel my stones in the center are too loosly connected. There are several big points on the board, marked by triangles, but I'm afraid to play them right now.]
;B[ki]C[I'm going to cut off this stone first., as I feel that my entire reductin of the middle hinges on it.]
;W[kq]
;B[jr]
;W[lr]C[I think this is small.]
(
;B[cc]C[*** See variation.
End of comments.]
;W[ba]C[Fracking monkey jump. This move should be forbidden in an extra rule.]
;B[bb]
;W[hi]
;B[ih]C[Connect this first for safety.]
;W[ca]
;B[in]
;W[hn]
;B[pi]
;W[pj]
;B[qh]
;W[ri]
;B[li]C[Reducing point by point....]
;W[fk]
;B[ej]C[Connect this for safety...]
;W[og]
;B[nh]
;W[ko]
;B[mj]
;W[lm]
;B[km]
;W[mk]
;B[ll]
;W[mm]
;B[lk]
;W[mi]
;B[ld]
;W[md]
;B[mj]
;W[qc]
;B[rd]
;W[mi]
;B[ph]C[I better connect this, as I'm not sure that this group lives if cut off now. I didn't see this, so I lose the ko.]
;W[mj]
;B[kj]
;W[ja]
;B[ia]
;W[ka]
;B[ib]
;W[kc]
;B[je]
;W[dg]
;B[bg]
;W[sc]
;B[sd]
;W[sb]
;B[ea]
;W[dc]
;B[ds]
;W[cs]
;B[es]
;W[da]
;B[fa]
;W[gg]
;B[gf]
;W[ff]
;B[hf]
;W[pf]
;B[mf]
;W[el]
;B[nf]
;W[of]
;B[ne]
;W[nd]
;B[pd]
;W[od]
;B[pc]
;W[pb]
;B[cd]C[Reductions seem to go well. I wonder if it's enough, as I haven't been counting since some time.]
;W[sg]
;B[sf]
;W[sh]
;B[qf]
;W[hp]
;B[gq]
;W[de]
;B[cb]
;W[db]
;B[ls]
;W[ms]
;B[ks]
;W[le]
;B[ke]
;W[im]
;B[dl]
;W[ps]
;B[qs]
;W[os]
;B[rq]
;W[ng]
;B[mg]
;W[ab]
;B[ac]
;W[fi]
;B[ei]
;W[gi]
;B[ek]
;W[em]
;B[dn]
;W[aa]
;B[fn]
;W[fo]
;B[jo]
;W[sm]
;B[so]
;W[io]
;B[jn]
;W[ik]
;B[hh]
;W[oh]
;B[pg]
;W[jk]
;B[pe]
)
(
;B[cb]C[*** Secures territory and threatens the life of the White group.]
)
)
(
;B[rh]C[*** Enlarges the room for eyes and threatens to go into the White sphere of influence.]
)
(
;W[rh]C[*** Makes territory and threatens the life of the Black group.]
)
(
;B[bm]C[*** Secures territory and threatens to jump or slide into the White sphere of influence.]
)
(
;B[bn]
;W[bo]
;B[dn]
;W[co]C[*** Secures territory with sente.]
)
(
;W[bn]C[*** Secures territory and threatens to jump or slide into the Black sphere of influence.]
)
(
;B[eb]
;W[db]
;B[fa]C[*** Secures territory and threatens to take some territory in the corner.]
)
(
;W[eb]C[*** Threatens to slide into the Black sphere of influence and to make territory in the corner.]
)
(
;B[nd]
(
;W[nc]
;B[od]
;W[md]
;B[ne]C[*** Makes territory and life.]
)
(
;W[od]
;B[nc]
;W[nb]
;B[mb]
;W[ob]
;B[lb]C[*** Makes territory.]
)
)
(
;B[fg]C[*** Threatens the life of the Whte group.]
)
)
(
;W[ih]
;B[jh]
(
;W[ki]
;B[hh]
)
(
;W[hh]
;B[ki]
)
)
)
(
;B[gg]
;W[fg]
;B[fh]
;W[eh]
;B[fi]
;W[eg]
;B[ee]
;W[de]
;B[df]
;W[ef]
;B[ei]
;W[cc]
)
(
;B[gf]
;W[ff]
;B[gg]
;W[fg]
;B[fh]
;W[eh]
;B[fi]
;W[eg]
;B[df]
;W[ee]
;B[de]
;W[eb]
)
(
;B[fg]
;W[gg]
;B[gf]
;W[ff]
;B[hf]
;W[eg]
;B[fh]
;W[eh]
;B[fi]
;W[ef]
;B[di]
;W[cc]
)
)
(
;B[gd]
;W[fe]
;B[ec]
;W[ed]
(
;B[cc]
;W[dc]
;B[db]
;W[gc]
;B[gb]
;W[hc]
;B[fb]
;W[hd]C[I think this looks good for White.]
)
(
;B[dc]
;W[cc]
;B[cb]
;W[bc]
;B[db]
;W[dh]
)
)
(
;B[cc]
;W[dc]
;B[cd]
;W[ce]
(
;B[be]
;W[bf]
;B[bd]
;W[cb]
;B[cf]
;W[de]
;B[bg]
;W[cg]
;B[af]
;W[df]
;B[bf]
;W[bb]
;B[ch]
;W[dg]
;B[ci]
;W[cl]
;B[ck]
;W[cm]C[Not sure about this either.]
)
(
;B[db]
;W[eb]
;B[cb]
;W[ec]
;B[be]
;W[bf]
;B[bd]
;W[df]
;B[ac]
;W[bb]C[Don't know if I can even get this to live...]
)
)
)
(
;B[co]C[Cutting here does not work.]
;W[cn]
;B[bo]
;W[bn]
;B[bp]
;W[bq]
;B[cr]
;W[br]
;B[dr]
;W[ao]
)
)
(
;W[cf]C[If white plays away, the D5 stone can get intor trouble.]
;B[co]
;W[cn]
;B[cp]
;W[dn]
;MA[cj][ck][dk][dj]TR[hn][ho][gn][go]B[fq]C[Because of Black 7, the normal extension of the C6 is prevented. White has to jump out into the middle to one of the squares marked with a triangle.]
)
)
(
;B[co]C[Normal variation.]
;W[cn]
;B[cp]
;W[dn]
;B[fq]
;W[dj]C[This would be normal, but I feel that White is getting toomuch on the left becuase of the D16 stone that is already in place.]
)
)
Main focus: Do not follow your opponent around. Look for moves that threaten the life of groups or secure life while threatening to take away potential territory. Look for double sente.