This is something you can try to become more ballsy. Deal a hundred total hands out on your table. 9-10 players. This should help you realize what people play when they limp. They are playing absolute crap. Isolate these retards with good healthy preflop raises and then take em down when you hit.

If this doesnt improve your confidence then try some SNG's. Play absolutely no hands except pocket pairs and the free BB till there's 5 people left. Hit and push. This might help too.