Because, as I am learning, your ability to care for others, to serve, to grow, depends on taking good care of yourself first.
And you can't put this on anybody else. What you eat, whether you exercise, how you feel about yourself, your attitude--it's all you. If you believe a relationship, a job, a responsibility, or a circumstance keeps you from taking care of yourself on any level, renegotiate or get out of it. Hard? Yes. Sometimes very. Worth the effort? Every time.
What you have to give is diminished when you don't prioritize your wellness. And you're worth the effort. The first, best effort.
But nobody else will believe that until you do.