The price of focus is accepting that worthwhile distractions still remain distractions.

The hardest distractions to refuse are the good ones, since there is no obvious reason to say no and it feels ungenerous. Focus means accepting that worthwhile things you decline are still worthwhile, and turning them down anyway. If you only refuse what is clearly bad, you have not really chosen anything.

Identify the worthwhile thing currently pulling at your attention. Decline it for now, without deciding it was unimportant. That distinction is what makes the refusal sustainable.