I play a conservative game as well, but one thing that happens when you play conservative is that you still need to push the other guy out when you have the best hand an make it really expensive for him to try and hit. If you let him in cheap, this is what happens:
He gets in cheap and misses, you get a small payoff.
He gets in cheap and hits, you get fucked.
So, in the long run, you get a bunch of small wins, and a few big losses. So even though you played "right" and he played "wrong", you end up even.
If, OTOH, when he's on a draw and you're ahead you make it expensive for him to play badly, here's what happens:
He often gets hit with big losses chasing, and once in a while he hits and you get fucked.
Last night was one of those "get fucked" nights for me. Typical of many frustrating hands: I'm on the button, SB is 30, BB is 60, UTG raises to 120, I raise to ?460? SB raises to something, 3 off us end up all-in. I have pocket Rockets, SB has pocket Cowboys, UTG has pocket 10's. K hits on the flop. A number of hands later, against the guy who won that hand I was all-in with AQ against his AJ, and a J hits. But I wouldn't play either hand any differently, and in the long run I'll win. Although neither of these is a good example, but this one is: at another game, I have AJd and raise to 3 times the BB. He re-raises, the guy in between us calls, I go all in and the both call. BB has A3 off, next guy has 86c. 2 clubs on the flop, 3rd on the turn. But both of them should be shot for going all in with hands like that. And I've seen both these guys at several tables, and don't remember seeing either of them ever finish in the money.