Leading means saying no to good ideas so the great one has room to breathe.

Good ideas are not scarce, which is exactly the problem. Every one you say yes to takes people, time, and attention away from what you actually decided to do, and a group carrying six good ideas does all of them at half strength. Saying no is not a judgement on the idea. It is protection for the one you already chose.

Look at what your group is carrying and find the good thing diluting the main thing. Set it down for now and say that out loud, including that it was a good idea. Put the recovered time into the one that matters.