I’m always tired. What am I doing wrong?

I’m an overall healthy 28 y/o male. I eat well, I try to be active (been more challenging lately). I’m in therapy, I am social, I am employed, I live alone. I don’t really drink or do drugs, heck I don’t even drink coffee with any regularity. I feel extremely exhausted. It seems like nothing I do recharges me in the slightest. I could spend an evening watching Netflix and “relaxing” and I often feel like I’m not using my time productively. I could go sit by the river and just listen to nature, and it does nothing. I feel like I’m running at a constant deficit and nothing is helping. It could be my retail job, but that’s harder to change. I’ve had more time off lately, which sucks financially but is appreciated for my health and well-being. I go on vacation and come back still exhausted. What am I doing wrong? Is this just how it feels to be an adult?