The short answer
You've built your sense of self on what you produce, so the moment you stop, you feel like you disappear. That's not the truth about you — it's a habit of mind. The work you do can matter without being the whole reason you matter.
You keep producing because stopping feels dangerous — not lazy, dangerous. Research on workaholism shows this pattern: working compulsively isn't just about loving work, it's about what stops feeling safe when you don't. The drive isn't really about the output. It's about managing a fear that without output, there's nothing left to stand on.
Marcus put it plainly: happiness that depends on what you make, or on how others see your making, is happiness you don't actually hold. You hand it to the next task, the next result, the next proof. He wasn't talking about ambition — he respected hard work. He was talking about the soul that forgets it exists apart from what it does.
This week, try one hour with nothing to produce. No task, no output, no self-improvement. Just exist in it. Notice what feeling comes up — that discomfort is the exact thing worth looking at. You don't have to fix it yet. Just see it clearly. That's where the real work starts.