@Welshman: Fudging is controversial to begin with, and fudging against your players is a quick way to start a player mutiny. I've done it a couple times when I knew that no harm would come of it, to give the players another whack at a fun enemy, but I really don't feel good about it. Sure, players can get tired of easy victories, but they sure as hell don't appreciate being robbed of their victories. If you get caught, a lot of players will never trust you again.
@bedlam: I don't really agree that PCs are the GM's creation, and even if I did, I still don't think it's a good idea to get attached to them. I'm all for the Rule of Cool and rooting for the PCs, for sure! But don't ever get hung up on a character (PC or NPC). Do that, and you're just going to try to steal the show from everyone else (and probably fail). Likewise, don't get hung up on a plot, or you're going to miss out on all of the cool other things that might happen with input from the whole group.