Ralph Waldo Emerson

http://www.theotherpages.org/unsort05.html

Nothing great was ever achieved without enthusiasm.

Be true to your own act and congratulate yourself if you have done something strange and extravagant to break the monotony of a decorous age.

and that quote in full

A foolish consistency is the hobgoblin of little minds, adored by little statesmen and philosophers and divines. With consistency a great soul has simply nothing to do. He may as well concern himself with his shadow on the wall. Speak what you think now in hard words and to-morrow speak what to-morrow thinks in hard words again, though it contradict every thing you said to-day. --Self-Reliance