So you didn't get done today what you wanted, so what? That doesn't mean you have to dwell on it. Tomorrow's a new day to begin again. To do the thing that you didn't get done or do the thing that you always wanted to do.
Let the day end along with the problems and worries that stressed you. Good and bad things happen, it is just a part of life. The trick is to let it go, keep looking forward, to a new day and a new beginning.