I recently had a 'below standard' day's flying. I did a x-country, and I wasn't overly impressed with my landing at the end of the home leg, even though my landings were fine the day before. I took the aircraft straight back up to do a couple of circuits so I could end the day on a good one, but I ballooned the next two, and ended up doing another 0.7 hrs before I was <reasonably> happy.
I suppose you just have to put it down to experience and try and learn from it. That's what hours building is all about. If you're sitting on the ground thinking about something that didn't go quite right in the air, then it couldn't have gone that badly, could it?
Pie