We’ve all heard this stated as if it’s the key to success: underpromise and overdeliver. Set expectations low, exceed them, and you’ll always come out ahead.

There are times when this makes sense. When you’re genuinely unfamiliar with the domain or uncertain about what’s possible, erring toward caution makes sense—you account for the unknowns, build in some margin, and sometimes you beat your conservative estimate. As an occasional tactic, it produces exactly the effect advertised: a pleasant surprise, a good impression, everyone satisfied.

But it shouldn’t be your default policy.

Try applying the same logic to other domains. Imagine a friend saying on their wedding day: “I’ll do my best to stay with you for at least a few years.” Or a coach walking into a new season: “Our goal is to get a few wins.” Or a founder pitching investors: “We’re hoping to raise a couple of rounds before we probably have to close shop.” In any of these contexts, the underpromise doesn’t sound like wisdom. It sounds like someone who has already accepted defeat before they’ve begun.

What these examples reveal is the true goal of “underpromise, overdeliver”: not to achieve something great or create delight, but to avoid disappointment.

Sadly, it doesn’t even work.

When you make a habit of underpromising, it affects how you approach the work. The gap between what you’ve promised and what you once thought you could actually do becomes a safety net—and safety nets eventually get used. Not always, and not consciously. But the knowledge that it’s there saps your conviction. By committing to the modest result, you privately commit to the safety net.

Then all too often, the modest result turns out to be not so modest after all. The safety net doesn’t catch you; you bounce off and hit the floor. Of course, this isn’t the end of the world: we all understand that sometimes things slip. The problem is that you weren’t aiming high to begin with. And worst of all is when you decide to be even more modest in the future—a safety net for the safety net.

Disappointment is inevitable. You will miss sometimes no matter how conservatively you’ve promised. Underpromising doesn’t change that; it just lowers the ceiling to what you might achieve. And a track record of hitting modest goals doesn’t set anyone apart anyway.

The alternative is simple. Ask yourself “How much can I accomplish if I truly do my best?”—not what seems safe, not what gives you cover, but what your honest best looks like. Commit to that, then do everything you can to deliver it. If you do this, how much more value could you create over the course of a year? A career? A lifetime?

This is not just me saying “work really hard at your job”; nor is it a call to make reckless promises or to project ambition you don’t genuinely feel. It’s about applying yourself in every aspect of your life and not hiding behind an imaginary disappointment shield. You may think it’s protecting you, but it’s very likely also holding you back.

Stop underpromising. Commit and deliver.