“Never say 'I can't.' 'I can't' is a limit, and life is about breaking through limits. Say 'I will' instead.”

“Do just once what others say you can't do, and you will never pay attention to their limitations again.”

“Science fiction writers, I am sorry to say, really do not know anything. We can't talk about science, because our knowledge of it is limited and unofficial, and usually our fiction is dreadful.”

“I'd rather look back at my past and say, "I can't believe I did that!" instead of saying "I wish I did that.”

“There is a limit to the amount of misery and disarray you will put up with, for love, just as there is a limit to the amount of mess you can stand around a house. You can't know the limit beforehand, but you will know when you've reached it. I believe this.”

“I can't change what's happened to me in my life, or make what's not occurred take place. But I can't say I like it, or accept it, or believe it's for the best. I don't and never shall, not even if I'm damned for it.”