By having reasonable boundaries, such as a baseline expectation that I won't spend more than 40 hours per week working. Then I have time to pursue other hobbies and interests without killing myself or my 8-9 hours of sleep every night.
Things also come and go in phases. Certain parts of the year are heavier on racing and then lighter on open source contributions. And vice versa.
Don't try to do it all at 100% at once. Doesn't work.