“Warren Buffett once said to us early at the [Gates] Foundation’s life, ‘Find your bull’s-eye of what you’re working on, and let the other things fall away. You’ll feel better if you keep your talents in that bull’s-eye, keep working those issues, and you’ll feel less bad about letting other things go,’” French Gates said in a LinkedIn interview last week. “And I think that’s true.”

This tidbit of guidance she received from the billionaire Berkshire Hathaway CEO around 2000—when she co-founded the Gates Foundation with her ex-husband Bill Gates—has stuck with her since. She said it’s essential for people to recognize what their professional boundaries are in business, and that saying “no” early on is important. French Gates even said in a Vanity Fair interview last year that she thinks it’s “so dumb” when CEOs romanticize forgoing sleep to get things done.

The thought of saying “no” and drawing lines can be daunting, but lingering on giving a negative response isn’t productive. Being upfront gives clarity to everyone involved—most times people understand that it isn’t personal, just business. 

“They don’t always [understand]. Most do, but if they come back again, you know it’s more about them than you,” French Gates said.

His advice on navigating tough decisions in philanthropy 

Warren Buffett didn’t only dish out some advice to French Gates on setting boundaries—he gave some recommendations on navigating tough choices in philanthropy as well. 

“Warren Buffett used to say to us, ‘Remember, you’re working on the problems that society has left behind. They are the hard problems. So keep trying to hit the home runs,’” French Gates said in the interview. 

“Yes, you’re going to have some misses, but spend most of your energy and resources there, and then spend some on today’s problems.”

Read more from Fortune

French Gates took this nugget of wisdom to heart—especially since Buffett was deeply involved in the Gates Foundation for years. The hedge fund billionaire served as a trustee and major donor to French Gates’ philanthropic organization from 2006 to 2021; by 2022, Buffett had collectively donated more than $36 billion to the foundation. 

For French Gates, it was difficult to know where to best put her efforts in philanthropy. Balancing the need for urgent humanitarian relief with stimulating systematic change in the long haul is a tall order. But harkening back to Buffett’s bull’s-eye advice, French Gates learned she had to keep her eyes on the overall mission at hand. That means funneling most money into long-term issues, and putting aside some to alleviate short-term crises. 

“It’s a really, really hard balance, and it’s something that I have thought about a lot,” she said. “You’re not going to save every baby coming down the river, but you’ll save more if you can go upstream some.”