Three.

The first is from a YC founder. I don't remember who, but he said "Always say yes." I tried that out for a while, and it has worked pretty well. A lot of where I am in my life is because I just said yes when I normally would have shrugged it off.

The second is from an essay by paul graham. "When given two choices, always choose the harder one." This one has become a mantra I say over and over again to myself. It hasn't failed me yet.

And finally, from Steve Jobs: "Listen to your intuition. It tends to know where you're going better than you do."

I think if I mix those three pieces of advice, I'll have a pretty respectable life.