How do I cope with being the one everyone relies on?

You can run a whole supplier base smoothly, holding everyone else's reliability together so the rest can count on it. That is a real strength, and it is also a heavy place to stand. When you are the one keeping it all from wobbling, you rarely get to lean on anything yourself. Of course you are tired. Being the reliable one is a gift you give, but it becomes a trap when it is silent and endless. If the whole thing rests on you alone, that is not only your burden to carry; it is a risk to the work if you ever stop. Your exhaustion is a signal worth heeding, not a weakness to push through. Start handing pieces off and building reliability that does not live only in you. Write down what you know. Train someone. Put systems in place so the base holds even when you step back. And let yourself lean somewhere too. You have spent a long time being the ground others stand on. It is fair, and it is wise, to make sure someone is holding some of it for you.