Your honest no is a kind yes to you and it's in the best interest of everyone.
Even if the folks who ask for your time quibble at your no, you benefit them by NOT going against your integrity. By NOT doing things half-heartedly, while wishing you’d said no in the first place.
So I invite you to borrow, steal or adapt any of the following —
Jamie Lee is an executive coach for smart women who hate office politics. She helps them get promoted and better paid without throwing anyone under the bus.