Endgame Help!

So the endgame is undoubtedly the worst part of my game (in my opinoin).  I assume there are some fundamental principles I constantly show blatant disregard of.  Can you guys help show me the flaws in my endgame of this match?  I really blew this one after move 31 (and probably multiple times before that, but specifically after this point)...

31 ...c5, now have a passed pawn, so push it

32 ...Bd7, gets the piece active, and controls c8 with the rook

34 ...Be6

35 ...a6 push the passed pawn

the rest is just really bad, I suggest playing with longer time controls

Thanks for the input guys, I think perhaps I was focusing too much on ways to mate him, I just assumed I'd win the game and didn't care about the pawns, then a couple blunders and I was in for it.