How do I make art for its own sake, not for an audience?

You have found something rare: the sense that the work is worth doing simply because it must be done. Hold onto that, because the world will constantly try to talk you out of it, offering applause in one hand and comparison in the other. When the worth lives in the making, you become free. A cold audience cannot ruin it. A silent room cannot cheapen it. You are answering to the work itself, and the work is an honest master — it asks only that you show up and tell the truth in your own hand. The danger is drifting back toward keeping score without noticing. So keep a small practice: at the end of each session, ask only whether you were honest to the work, not whether it will be liked. Let that single question be your measure. It will keep you pointed at the making, where the worth actually is.