I know better. I teach this. I preach it. STOP painting when you are tired, even if you are just a few strokes from completion. 11:30 pm...almost done...3:00 am ... complete ruin. That last brush stroke turned into a touch here and there and then "how can I fix this?" and by 3:00am it was beyond repair. After realizing that this wonderful painting was beyond hope, I covered it with a towel, set it back on the easel overnight while I mourned the loss. I couldn't bring myself to pull the towel off the painting until I had a very strong cup of coffee this morning. I guess there was that small hope that maybe it wasn't as bad as I remembered, maybe I could salvage it or even better, maybe it would end up being a "happy mistake" and be a creative work of genius. Nope. Awful. So I will let it go. The best way to cure the grief of a mistake is to start a new painting immediately.