A life spent chasing the mythical state of being able to do everything is less meaningful than a life of focusing on a few things that count.
I read / leaf through Essentialism with a frequency that's rare for me. I'd give it a read if you want more advice on the above.
If everything that's being thrown at you matters to you, that means that nothing really matters to you. This week alone, I said no to two speaking engagements because I had more important things to do. I try to be incredibly strict in how I spend my time, moreso when I am under a lot of work load. If that means disappointing people along the road because I don't do what they ask of me, so be it.