Depends on the game. Like for example, I see that I'm struggling a lot in a boss fight, even if I can beat it, the fact that I've had to struggle so much to do so is an issue. So I'll reset and go build up my characters more. In Suikoden, during the war type battles, if one of your characters died, you couldn't use them anymore, so I would reset. If it involved me permanently losing a character, always reset. Other than that, I don't really do it that much.