You only live once, but if you live life right the first time once is enough! That's my personal motto but I collect quotes so here's a couple that might fit.
"Don't let the fear of the time it will take to accomplish
something stand in the way of your doing it. The time will
pass anyway; we might just as well put that passing time
to the best possible use."
- Earl Nightingale, Author and Businessperson
"Instead of seeing the rug being pulled from under us,
we can learn to dance on a shifting carpet."
- Thomas Crum, Author and Speaker
"A happy person is not a person in a certain set of
circumstances, but rather a person with a certain set of
attitudes."
- Hugh Downs, Television Newscaster
"A man can fail many times, but he isn't a failure
until he begins to blame somebody else."
- John Burroughs, Naturalist
"Don't judge each day by the harvest you reap, but by the
seeds you plant."
- Robert Louis Stevenson, Author
"When you have a great and difficult task, something perhaps
almost impossible, if you only work a little at a time, every day
a little, suddenly the work will finish itself."
- Isak Dinesen (pseudonym for Karen Blixen), Danish Writer