Saying no may take some people aback but ultimately they will respect you for knowing and sticking to your priorities.
We are not only the work that we do. We are also the company we keep, the hobbies and projects that we cultivate, and the activities that we enjoy. Make time for these things, and your work self will reflect the benefits.
Visualize the end result so you can see it and visualize the action to get to the end result.