Making the choice to be optimistic is always worth it, especially when it’s the more difficult decision to make. As Bob Iger, who leads Disney, puts it, optimism is the ability to focus on what matters—steering your team towards the best possible outcome, and moving forward in spite of setbacks. It also means letting go of what doesn’t matter: despair, defensiveness, victim mentality, self-preservation.

Deluding yourself can give you good short-term fuel. It doesn’t last very long though. Inevitably, your delusions bump up against what’s actually happening in the real world. “The bigger the fantasy you live, the more painful the inevitable collision with reality,” Will Smith writes in his memoir. “Reality is going to pay you back in equal proportion to your delusion.”

If you’re going to be audacious and make big bets, you also need to be honest with yourself and your team about how plausible the best outcome really is.

There is a difference between practicing optimism and getting caught up in your own delusions. Sometimes, even really smart people get these two things mixed up, when they couldn’t be more different.

Optimism earns confidence. Delusion borrows your confidence, and rarely pays it back.