Why do I only notice the toll of work when my body breaks down?

You push your body for the work and only feel the cost when something finally gives out. This is common and it is dangerous, because by the time the body breaks the debt has been building unseen for a long time. The breakdown is not the beginning of the problem. It is the bill arriving. The body sends quieter signals long before it breaks, the tight sleep, the constant fatigue, the small pains you push through. You have trained yourself not to hear them, probably because hearing them felt like it would cost you at work. But ignoring the signal does not make the damage stop. It just moves it out of sight until it cannot be ignored. Start listening to the small signals now, before the large one comes. Once a week, actually check in: how is my sleep, my energy, my body. Treat a warning sign as information to act on, not weakness to override. Your body is not the enemy of your work. It is the thing doing the work, and it cannot be replaced.