There have been many people that own a psp console, that have played for hours and hours to complete there game and there save gets corrupted and all that hard work has gone to waste. When a psp console corrupts a game save data file, in simple terms it basically means, the memory stick has half of the data and the other data has got either deleted or damaged.
There are three main reasons why a psp console corrupts game save data:
1)You have installed custom firmware onto you psp, there were a bug in some older custom firmwares, such as 5.50 GEN D2 that caused game data to get corrupted. I suggest if your psp is running cfw firmware, always regularly check for any latest updates, as they always new features and improvements cfw developers create.
2)When the psp is saving the data onto the psp memory stick and you power off the psp, or remove the battery pack.
3)You removed the memory stick from the psp, when the psp is saving game data onto the memory stick.
If your psp game save is corrupted, you might be able to fix it, below is a blog post you might find useful: