One of the biggest mistakes that I see people make is they don’t want to learn from someone who has a character blemish or a worldview that doesn’t align with theirs. Seneca captured the right approach when he said in On the Tranquility of the Mind, “I shall never be ashamed of citing a bad author if the line is good.” Or, as Cato the Elder put it,

Good judgment is expensive, but poor judgment will cost you a fortune.

F. Scott Fitzgerald once said, “The test of a first-rate intelligence is the ability to hold two opposed ideas in the mind at the same time, and still retain the ability to function. One should, for example, be able to see that things are hopeless and yet be determined to make them otherwise.”

One of my exemplars is Charlie Munger, the billionaire business partner of Warren Buffett. He raised my standard for holding an opinion. One night at dinner, he commented, “I never allow myself to have an opinion on anything unless I know the other side’s argument better than they do.”

A bad process can never produce a good decision. Sure, it might result in a good outcome, but that’s different from making a good decision.

There is need, I insist, for someone against whom to measure our way of life; unless you have a ruler, you can’t straighten what is crooked.

Rarely are you making decisions that have a 100 percent chance of success. And the kind of decision that has a 90 percent chance of success still has a bad outcome 10 percent of the time. What matters are results over time and ensuring that 10 percent of the time won’t kill you.

Pillemer asked one of his interviewees for help understanding the source of her happiness. She thought about it and answered, “In my 89 years, I’ve learned that happiness is a choice—not a condition.”

the process principle: When you evaluate a decision, focus on the process you used to make the decision and not the outcome.