Last week I sent a very firm but humble "no" to someone asking for some of my time. I had never quite done that before. It felt strange at first but then I realized that I stood behind my reasoning.
Saying no is not about keeping the goods scarce to increase demand or creating guardrails against the abuse of your time. Saying no is about coming to truly respect both your time and someone else's. I did not say no because I was tired, I said no because I am energized by the other ways I will be using that time. I did not say no because I did not want to do what was asked, I said no because I realized it would not have been the best use of both my time and the time of the other party involved. I challenge you to think about if you are saying no enough and also why you will be saying no at all.