> I think, as op also insinuates, it is all about acceptance.

I second this. From my experience you have to START WITH ACCEPTING the status quo and honestly looking at it without judging or being ashamed. It helps me to tell myself: "This is not terrible. I am alive. I have a job. My body is still working OK."

From there FOCUS ON THE DELTA: What can I do today that will bring me into a slightly better position tomorrow.

Avoid thinking about the past ("I ate too much today.", "I did not exercise all week."). This is done. No way to change it.

Don't set high expectations. You only need to know where you want to be, and that you are going into the right direction. It does not matter much if you arrive there in one week or in five years.