Similar thing happened with Far Cry 2. Accidently saved over my usual slot (nearly done with the game), with a new character I made for kicks. The thing is, I hate Far Cry 2. I just felt I had to beat it, but once I did that, I said screw it, and never picked it up again.
EDIT: And then there was the time where I successfully ambushed Gaul's last family member, in Rome: Total War, with a numerically inferior army.
But with some careful tactics, and superb commanding (if I do say so myself) I managed to defeat the Gauls, destroy their nation, and take the day..... Until a tree decided to fall on a nearby transformer causing a neighborhood blackout...