from Self-Reliance, by Ralph Waldo Emerson
(full text of essay can be found at emersoncentral.com/selfreliance.htm)
Insist on yourself ; never imitate. Your own gift you can present every moment with the cumulative force of a whole life's cultivation ; but of the adopted talent of another you have only an extemporaneous half possession . . . . Do that which is assigned to you, and you cannot hope too much or dare too much.
excerpts from other Emerson writings:
finish each day and be done with it. you have done what you could. some blunders and absurdities have crept in; forget them as soon as you can. tomorrow is a new day. you shall begin it serenely and with too high a spirit to be encumbered with your old nonsense.
To laugh often and much, to win the respect of intelligent people and the affection of children, to earn the appreciation of honest critics and endure the betrayal of false friends, to appreciate beauty, to find the best in others, to leave the world a bit better, whether by a healthy child, a garden patch... to know even one life has breathed easier because you have lived. This is to have succeeded!