In Final Fantasy Tactics, there's two successive battles before you fight Velius. You're given the option to save your game in between the two fights, which I did. The problem is that the fight against Velius is fucking brutal. I got my ass handed to me over and over and thanks to saving right before the fight, I didn't have the option to go back to the world map to level. I thought I'd have to start over from the beginning of the game (which would have meant many many hours lost) but I finally managed to win with some tweaking of my party and a lot of luck.
That series of battles probably caused people the most rage inducing moments of the entire game. I made that mistake too and was one of the unlucky ones who ended up having to start the whole game over
I still love the game though.