Note to self: If you hit a target with a torpedo at close range, turn away instead of continuing toward him with your mind in neutral. If a fire sets off a secondary explosion you don't want to be too close. Also (same patrol!) if you're doing a night surface attack and pass a large tanker (that might be full of avgas) within 300 yards, it's an incredibly bad idea to open up with the deck gun at that range.
Sometimes I do more damage to me than the enemy does.