With some games I used to make a bunch of save files at different stages when I am not sure what I should be doing, then I just keep on playing whatever advance with minimum trouble. Then when I was kind of near the end of one game, I thought I'd delete all my extra saves on memory card to save space (this was PSX not PS2) and ended up erasing my main save.

I think I broke a PSX controller also. But I will not say how. It was a different game and kind of unrelated to the save files being deleted.