"Finish each day and be done with it. You have done what you could. Some blunders and absurdities no doubt crept in; forget them as soon as you can. Tomorrow is a new day; begin it well and serenely and with too high a spirit to be cumbered with your old nonsense."
I like this one even more. One of my own sayings I keep on a post-it at my desk is: "Today is what you make it. And tomorrow is always a new day." This quote by Emerson seems (to me) to go hand in hand with that mentality. Instead of beating yourself up for mistakes you made or setbacks that may have happened, instead of berating yourself for being the way you are, and instead of worrying over what happened in the course of the day—"finish each day and be done with it." There is no better advice than that. As Emerson says, "You have done what you could." Things may have happened that you didn't like, but forgetting them as soon as you can is a much better choice than dwelling on them and thus allowing them to hinder your progress for the days to follow. Each new morning, focus not on the day that has passed, but begin the new day "serenely and with too high a spirit to be cumbered with your old nonsense." When the day begins, it is new and fresh and clean and blank. Don't mar such a glorious thing with bad feelings from the previous day; march on and make the day what you want it to be.