One of my favorite quotes are,
"When you are courting a nice girl an hour seems like a second. When you sit on a red-hot cinder a second seems like an hour. That's relativity."-Albert Einstein
Here's another favorite of mine by a true hero,
"Every man dies. Not every man really lives."-William Wallace
And the last two are in my signature, so you've probably seen them already

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"Be not afraid of greatness: some are born great, some achieve greatness, and some have greatness thrust upon them."-William Shakespeare
"The whole art of war consists of guessing at what is on the other side of the hill."-Arthur Wellesley
He who fights with monsters should be careful lest he thereby become a monster. And if thou gaze long into an abyss, the abyss will also gaze into thee. - Friedrich Nietzsche