One thing to consider is that if there's a reasonable invasion, it was never territory to begin with. Imagine you have a position like so:hl782 wrote: 3) When someone invaded my territory, I used to think - oh man there goes half my territory. But, now i realized that by invading, my opponent is creating a weak group for me to target. Using this, and point #1 above, I realized that If i can make more profit from attacking the weak group than the territory i lost, getting invaded isn't that bad after all.
When white plays
or a similar move, is white taking your territory away? I'd say no, because with two open skirts, it's reasonable to assume that white will get a monkey jump on one side or the other. Similarly, if you set up a big moyo, and your opponent decides that he doesn't need to invade or do anything about it, despite being behind, he's lost the game already. There isn't territory there until your opponent no longer has aji in the area. Until then it's just potential, and a threat that your opponent needs to deal with in some way or other. This might be invasion, but it might also be reduction or having a competing position somewhere else. Either way, they need to and will do _something_, so it behooves you to have a plan to turn it into territory either locally, or somewhere else on the board (as by attacking an invading group).
premature endgame sente will strengthen the opponent and destroy middle game potential to attack
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is a showcase of the infamous "squeezing out the toothpaste": 
is quite well judged. White plays passively.
, 
(raw peep).
at D6 and wrecking White's shape? You get a poor result in this corner, but White has played badly.
) and you shouldn't be disagreeing with it. Improvement is not linear, a game of go is the sum of a lot of decision-making (say, 50 decisions per game, where you choose "where and/or what"). You may have aced 49 of these, making this one of your best games and screw the 50th. You lose, but you'll have improved. If you only focus on results (and not on the process itself of improvement) your "playing mood" will go up and down (after all, once your rank is more or less stable winrate is really close to 50%) constantly.