I never, ever cheat any of my players. We all know that our game is fairly lethal, and to be totally honest, I think that cheating cheapens the experience.
We're playing D&D to play a band of plucky adventurer-theives looking for treasure and trouble, not to be a movie star. If we wanted to have a wire-fu fantasy beat-em-up where we always win, we probably wouldn't bother with the dice at all.
I'm not degrading diceless systems either, don't get me wrong. Sometimes that's exactly what you want to play, and that's fine too. But if that's what you want, why even pretend to use the dice as fate/luck in the first place?