David Sparks in a post about his No Journal:
Moreover, I have no doubt that some of the projects I was truly passionate about ended up substantially less awesome because of my inability to say no to other things. Put simply, saying yes too often means that you will, necessarily, be mailing it in on everything.
Another benefit of saying no is that it reminds me how special those things are that make the cut. Whether it is writing an article, giving a killer presentation, or just taking a walk with my wife, those are items that I’ve chosen to do because they are so special. It makes mindfulness easy.
David takes saying “no” to a whole new level by implementing an actual system. It may sound a bit extreme, but the importance of saying no cannot be understated. If you said yes to everything, you wouldn’t have time for anything. The rejection of things that add no real value to your life is a cornerstone of minimalism: do what makes you happy, and eliminate the rest.