Saying yes to everything isn’t a work ethic. It’s how you end up doing five things badly.

Agreeing to everything looks generous and ends up unreliable. There is a fixed amount of time and attention, so every extra yes quietly lowers the quality of all the earlier ones, and the people counting on you experience that as broken promises rather than enthusiasm. A clear no protects the yeses you have already given. Capacity is a real thing, not a measure of your character.

Before you agree to the next request, check what it is replacing in your week, because something always gets displaced. Say no to one thing you would normally accept, briefly and without a long explanation.