As an athlete and a human being I think it is good to have a "short" memory about a lot of things. It usually takes me a good night's rest to move on from something that was bugging me. In athletics it also applies.
I have one athlete I work with who has a very LONG memory when a workout goes well or poorly. As an actor friend of mine said, "Yesterday is history. Tomorrow a mystery. That's why they call today the present." I like it a lot. Forget the "bad" workout as soon as possible. As I told this athlete, "Why did you think that workout was bad? Did you understand my expectations for this workout?" When I explain that I was looking for heart rates, splits, MPH, RPMs and wattage, etc. and my athlete hit them all; I explain that I am actually quite happy about the workout. Even if it "felt" awful - feeling awful is part of training. You aren't going to feel sprite every day. Gosh, I hope not. My athletes should feel a bit tired until we get to their A race.
Nailing a workout isn't necessarily feeling great while doing it.
Another great athlete I work with will relive a great workout for months unless I re-focus them on today. I have to admit that is a lot harder to leave the great workouts "in the bank" and focus on suffering today.
Each workout is ONE opportunity for greatness. The workout itself should be graded as just that - ONE workout. Don't get too excited or down from the experience.
One mile at a time. One workout at a time. We become great as a collection of these come together as a whole.