There are many more, but here are a few of my favourites

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The beginning of love is to let those we love be perfectly themselves, and not twist them to fit our own image. Otherwise we love only the reflection of ourselves we find in them. -Thomas Merton, No Man Is an Island
All the kids kept trying to grab for the gold ring, and so was old Phoebe, and I was sort of afraid she'd fall off the goddam horse, but I didn't say anything or do anything. The thing with kids is, if they want to grab for the gold ring, you have to let them do it, and not say anything. If they fall off, they fall off, but it's bad if you say anything to them. -Holden Caulfield, Catcher In the Rye
Friendship is a single soul dwelling in two bodies. -Aristotle
Watch your thoughts; they become words. Watch your words; they become actions. Watch your actions; they become habits. Watch your habits; they become character. Watch your character; it becomes your destiny. -Lao Tze
You must be the change you wish to see in the world. -Gandhi
We are what we repeatedly do; excellence, then, is not an act but a habit. -Aristotle
Do not seek to follow in the footsteps of the men of old; seek what they sought. -Basho
Try a thing you havent done three times. Once, to get over the fear of doing it. Twice, to learn how to do it. And a third time, to figure out whether you like it or not. -Virgil Garnett Thomson
If the lessons of history teach us anything it is that nobody learns the lessons that history teaches us. -Anonymous
Believe those who are seeking the truth. Doubt those who find it. -André Gide
Better to write for yourself and have no public, than to write for the public and have no self. -Cyril Connolly
The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails. -William Arthur Ward
Computers are useless. They can only give you answers. -Pablo Picasso
What the world needs is more geniuses with humility, there are so few of us left. -Oscar Levant
Those who believe in telekinesis, raise my hand. -Kurt Vonnegut
There is nobody so irritating as somebody with less intelligence and more sense than we have. -Don Herold
Sometimes I worry about being a success in a mediocre world. -Lily Tomlin
It is amazing what you can accomplish if you do not care who gets the credit. -Harry Truman
I quit therapy because my analyst was trying to help me behind my back. -Richard Lewis
Never argue with a fool, onlookers may not be able to tell the difference. -Mark Twain
The tooth fairy teaches children that they can sell body parts for money. -David Richerby
My friends tell me I have an intimacy problem. But they dont really know me. -Garry Shandling
Never be afraid to laugh at yourself, after all, you could be missing out on the joke of the century. -Dame Edna Everage
Time flies like an arrow; fruit flies like a banana. -Groucho Marx
Those are my principles. If you dont like them I have others. -Groucho Marx