Irritated by missed judgements in movements, wrong battle decisions, or a 80% sure hit that just missed (frustating, isn't it?)...
For this to work, be sure you are able to save the battle before the mistake is to be made! (Save always after every turn if in doubt!; the "In-Battle save" option is activated by clicking on the map, not on any character, and then highlighting the last name-option on the Main status bar), then:
Soft Reset - Press and hold together the following: L1+L2+R1+R2+Select+Start
Once the screen turns black (don't wait for the BANBRESTO logo to appear), activate:
Quick Reload - Press and hold L1+L2+R1+R2+Select+0 (Circle)