Here's some of my favorites! They may not all seem so positive, but they help me feel understood, like I'm not crazy:
"The only way to deal with an unfree world is to become so absolutely free that your very existence is an act of rebellion." (Albert Camus)
"Don't walk behind me; I may not lead. Don't walk in front of me; I may not follow. Just walk beside me and be my friend." (Albert Camus)
"In the depth of winter, I finally learned that within me there lay an invincible summer." (Albert Camus)
"Be the change that you wish to see in the world." (Mahatma Gandhi)
"An eye for an eye makes the whole world blind." (Mahatma Gandhi)
"Speak only if it improves upon the silence." (Mahatma Gandhi)
"We have enslaved the rest of the animal creation, and have treated our distant cousins in fur and feathers so badly that beyond doubt, if they were able to formulate a religion, they would depict the Devil in human form." (William Ralph Inge)
"No one is more of a slave than he who thinks himself free without being so." (Johann Goethe)
"Do unto others 20% better than you would expect them to do unto you, to correct for subjective error." (Linus Pauling)
"A dreamer is one who can only find his way by moonlight, and his punishment is that he sees the dawn before the rest of the world." (Oscar Wilde)
"My peers, lately, have found companionship through means of intoxication - it makes them sociable. I, however, cannot force myself to use drugs to cheat on my loneliness - it is all that I have - and when the drugs and alcohol dissipate, will be all that my peers have as well." (Franz Kafka)
"The truth is like a lion; you don’t have to defend it. Let it loose; it will defend itself." (Augustine of Hippo)
"In the end, we will remember not the words of our enemies, but the silence of our friends." (Martin Luther King, Jr.)
"Your vision will become clear only when you can look into your own heart. Who looks outside, dreams; who looks inside, awakens." (Carl Jung)
"If God exists, he has to beg my forgiveness." (written on one of the walls at a concentration camp)
"I saw the angel in the marble and carved until I set him free." (Michelangelo)
"I intend to live forever, or die trying." (Groucho Marx)
"I am pursuing Truth, and am indifferent whither I am led, if she is my only leader." (Benjamin Rush)
"There are two ways of spreading light: to be the candle or the mirror that reflects it." (Edith Wharton)
"For me, the most ironic token of the first human moon landing is the plaque signed by President Richard M. Nixon that Apollo 11 took to the moon. It reads, ‘We came in peace for all Mankind.’ As the United States was dropping seven and a half megatons of conventional explosives on small nations in Southeast Asia, we congratulated ourselves on our humanity. We would harm no one on a lifeless rock." (Carl Sagan)
...and my all-time favorite, life-defining quote:
"It is no measure of health to be well adjusted to a profoundly sick society." (Jiddu Krishnamurti)