The most expensive word in your vocabulary might be “sure.”

A casual yes is the cheapest thing to say and the most expensive thing to have said. It takes half a second, avoids a small awkwardness, and commits an evening, a Saturday, a month of your attention that you had other plans for. The cost lands later, on a version of you who was not consulted. By then the only options are going or letting someone down.

Buy yourself a delay. Say you will check and come back, then answer from a calendar rather than from the pressure of the moment. Most people accept that easily, and it turns a reflex into an actual decision.