"NO." -- A powerful word that is vastly under-utilized.
Time and energy are two of our most precious resources. They are both finite, and in the case of time, it's not replenish-able. You can take a day off and recoup your energy, but once that five minutes is gone, it's never coming back. And in regards to time, recent studies show that just 30 seconds of distraction can take as much as fifteen minutes to regain the degree of focus you had pre-distraction. So how we use these assets is incredibly important. So the things we say "yes" to matter all the more in light of this. While in many cases I'd posit that "best is the enemy of good", I'd say in this one context, the rule is entirely reversed. Here's what I mean:
Saying yes to too many "good" things distracts us from investing in what is ultimately best.
How does this happen? How we we end up in the place where we have so much "good" that's happening that we end up missing out or shortchanging the things we say really matter? It's because we haven't weighed that "yes" against our goals. We've allowed our clarity to become clouded. It could be because that "thing" we want to say yes to is a passion, but isn't aligned with our actual goals. Or it could be that the idea we just heard would make us a quick buck, but cause us to miss important deadlines for the bigger things that matter. But in any capacity... the more good things we pile on, the less room we have to keep laser focused on what is actually best.
So say it with me... "No." ... Say it again... "NOOO." It stings. But it's necessary. Stop doing good things and do only best things.