Learning to say, "No" is probably the hardest thing to do in business and art. Here is some more reading up to help us all with that.
“Time is the raw material of creation. Wipe away the magic and myth of creating and all that remains is work: the work of becoming expert through study and practice, the work of finding solutions to problems and problems with those solutions, the work of trial and error, the work of thinking and perfecting, the work of creating. Creating consumes. It is all day, every day. It knows neither weekends nor vacations. It is not when we feel like it. It is habit, compulsion, obsession, vocation. The common thread that links creators is how they spend their time. No matter what you read, no matter what they claim, nearly all creators spend nearly all their time on the work of creation. There are few overnight successes and many up-all-night successes.
Saying “no” has more creative power than ideas, insights and talent combined. No guards time, the thread from which we weave our creations. The math of time is simple: you have less than you think and need more than you know. We are not taught to say “no.” We are taught not to say “no.” “No” is rude. “No” is a rebuff, a rebuttal, a minor act of verbal violence. “No” is for drugs and strangers with candy.”