Throughout the game, B played fast and loose, attacking often but rarely taking time out to defend cutting points or make a base for a weak group. Take a look at the position after move 48. The lower left group at G4 has not made a base, the lower right connection between O5-Q6 can be cut, and the upper right string of stones is too thin to be called a wall. At this point, I think the best plan for B is to defend some of these weaknesses, build up strength before launching another attack. Connecting solidly around O7 would be good. Or consider K3, making a base for the lower left, attacking the W lower side, and indirectly defending the lower right.
The attack at move 49 seems dangerous, at least before some of the preparations suggested above. The continuation up to move 58 gives B a huge moyo, but the stones below become very weak. Playing like this is possible -- B gets enough territory above to win, provided he does not get killed below. But to be consistent, B *must* extend at G10, and if W continues to push for another move or two, B must continue to extend. When B takes time out to defend at G6, letting W crush the moyo with G10, the B strategy has failed. Once you have started a sequence like this, play it out consistently! If you find a way to make sabaki below, it will be a satisfying win
If those stones all die, you will hopefully learn to be more cautious in your attacks in the future