Whenever a list of the best quotations is compiled most (if not all) of these will be on it.

o “Live as if you were to die tomorrow. Learn as if you were to live forever.” Mahatma Gandhi

o “That which does not kill us makes us stronger.” Friedrich Nietzsche

o “Be who you are and say what you feel, because those who mind don’t matter and those who matter don’t mind.” Bernard M. Baruch

o “We must not allow other people’s limited perceptions to define us.” Virginia Satir

o “Do what you can, with what you have, where you are.” Theodore Roosevelt

o “Be yourself; everyone else is already taken.” Oscar Wilde

“This above all: to thine own self be true.” William Shakespeare

“If you cannot do great things, do small things in a great way.” Napoleon Hill

o “If opportunity doesn’t knock, build a door.” Milton Berle

o “Wise men speak because they have something to say; fools because they have to say something.” Plato

o “Strive not to be a success, but rather to be of value.” Albert Einstein

o “Two roads diverged in a wood, and I…I took the one less traveled by, And that has made all the difference.” Robert Frost

“Do not let what you cannot do interfere with what you can do.” John Wooden

o “Whenever you find yourself on the side of the majority, it is time to pause and reflect.” Mark Twain

o “I haven’t failed. I’ve just found 10,000 ways that won’t work.” Thomas Edison

o “Cherish those who seek the truth but beware of those who find it.” Voltaire

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I highly recommend The Yale Book of Quotations, Edited by Fred Shapiro. In my opinion, it is the finest single source.