The American poet and abolitionist Ralph Waldo Emerson is considered a leading light in the Transcendentalist movement of mid-19th Century.
In April of 1854, Emerson wrote a letter to his daughter Ellen (who was 15) about maintaining a positive attitude on a daily basis. In essence, how to not be encumbered by the past.
Below are his words with modern punctuation to make it a smoother read.
You must finish a term, and finish every day and be done with it. For manners, and for wise living, it is a vice to remember.
You have done what you could. Some blunders and absurdities no doubt crept in. Forget them as fast as you can. Tomorrow is a new day.
You shall begin it well and serenely, and with too high a spirit to be cumbered with your old nonsense.
This day for all that is good and fair. It is too dear with its hopes and invitations to waste a moment on the rotten yesterdays.