I once thought that exercise was a duty and that, if I did not exercise, this revealed a defect of will. I thought too that indolence was a condition to which all humanity tends and that this tendency must be met by a steely will.
Thus when I did not exercise, I felt guilty; and I looked down on others who were in poor shape.
I now reject this. If we are out of shape, this is not the result of a moral defect. It is rather the result of disease, and in most of us this disease has its root cause in malnutrition.
If we were to eat right, we would be more energetic; and if we were more energetic, we would quite naturally and inevitably rise up off our asses and put our bodies in motion.
I don't mean to say that we'd run to the gym. Some will. Some won't. I don't. But we will become more active. We will feel a need to rise up, to move the legs and arms and likely to seek out the sun. (I thus suggest that we give up on the concept of exercise. It has about it an air of duty, of obligation and so of difficulty. Let us instead speak simply of activity.)
The human body is designed for activity. It was made to move, to lift, to run and to sweat. This is no less natural to it than is eating or breathing. We should feel the need for it; we should take joy in it. And we will if all goes right. If the body sinks into indolence, this is the result of profound dysfunction, and I contend that this dysfunction is almost always brought on my improper diet.
Eat as our first ancestors ate. Eat a Paleolithic diet. You'll want to get up out of that chair and get the body in motion. (I'm off to take a walk. Not because I think I should but because I feel an itch to move.)