“Calvin: There's no problem so awful that you can't add some guilt to it and make it even worse!
p100”

“Calvin: You know, Hobbes, some days even my lucky rocketship underpants don't help.
p33”

“Everyone makes mistakes, even if some are worse than others. Accidents happen.”

“Anytime there is a problem in a relationship, you should first see it as your own fault. Even if others are to blame, you will only add to the problem by considering them to be at fault.”

“Guilt and no guilt: these were the worst things. The only thing worse than the guilt was the fear of getting caught.”

“No. Never. I have to try my best or I'll become worse and worse. Even if I can't make up with them. Even if they all ignore me. I still have to try my best.”

“The government solution to a problem is usually as bad as the problem and very often makes the problem worse.”

“Calvin, what kind of trouble are you planning to make?”
“No trouble at all,” said Calvin, annoyed. “Why do you think I want to cause trouble?”

“This ain't for the best.
My reputation's never been worse, so
You must like me for me.
We can't make any promises Now can we, babe.
But you can make me a drink.”

“It's awful bad luck to bring a woman aboard the ship."
"It's awful worse luck not to.”