How do I keep going when I'm always the one holding everything together?

You are the one who holds it together, and everyone knows it, which is exactly why it never stops. When you are reliable, more gets placed on you, until being the keystone becomes a weight you carry alone. The tiredness is not weakness. It is the honest result of being load-bearing for too long without relief. Being able to hold it all does not mean you must. Start letting others carry real pieces, even knowing they will do it differently, even a little worse at first. Every time you rescue a thing yourself, you teach the people around you that you will always catch it. Let a few things be caught by someone else, and watch them rise to it. And guard your own reserves like they matter, because they do. The person who holds everything together is worth protecting, and often the only one not protecting them is themselves. Rest is not a reward you earn after the work; it is what keeps you able to do the work at all. Put yourself back on the list of things you keep standing.