Story highlights Bill and Melinda Gates: 10 years ago, Warren Buffett gave us billions of dollars to try to make the world better

His model of optimism -- not just hoping for the best but making it happen -- has been an inspiration, they write

The authors are co-chairs of the Bill & Melinda Gates Foundation. Their 2017 Annual Letter, from which some points in this article are adapted, is available at www.gatesletter.com. The opinions expressed in this commentary are theirs.

(CNN) Warren Buffett is one of the best loved people in the world -- and it's easy to see why. He's jovial and friendly. He's funny and wise. He makes people feel good about themselves. But he has one quality that fuels all the others: Warren is the most upbeat, optimistic person we know.

He's optimistic about the country, about the future and about you. No matter where things are right now, he knows in the long run they're getting better. You doubt it? Don't bet against it; he's made billions investing in that belief. The great thing about Warren's optimism is you can't hear him share a story, tell a joke or say hello without picking up some of his optimism yourself.

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That's why it feels so good to be around him.

Some people might say, "I'd be optimistic, too, if I'd had his success." But we think that has it backward. Warren's success didn't create his optimism; his optimism led to his success. Because optimism isn't a belief that things will automatically get better; it's a conviction that we can make things better.