Not getting enough sleep for a year due to responsibilities to the point where I wouldn't (and still don't) feel refreshed by 8-10 hours sleep. A sure-fire sign of adrenal fatigue but I have high cortisol rather than low cortisol and the problem for me is too much copper and estrogen in my body, slow liver and thyroid function and low ceruloplasmin.
Even when you know what is wrong with you, it is very hard to fix it.