Ben Horowitz: Every founder experiences doubt — even Mark Zuckerberg “Congratulations on betting on yourself,” a16z co-founder Ben Horowitz tells an audience full of founders. “Your job is to make your bet payoff. You believed in yourself enough to do it, and there are going to be many times when you question that bet. But that gets you nothing.” Ben offers the following advice: “You just have to do your thing, keep going, and focus on what you can do. The doubts are going to be there, but ignore the doubts. The worst doubts aren’t the ones people put on you; they’re the ones that you put on yourself. Every entrepreneur has them. I spent a lot of time with Mark Zuckerberg when he was 22 years old, and he had tremendous doubt about whether [Facebook] was going to make it. Everybody has that.” He continues: “It’s not what you feel. It’s what you do. So just focus on what you do. You’re going to feel scared. If your guts aren’t boiling, you’re not even trying at these things. Don’t worry about it.” Source: @speedrun (Oct 2025)