Oh wow that sounds exactly like me. I’ve just been promoted to a job that was three people in November. Instead of feeling motivated to take on three times as much work I feel like I’m cocooning. Instead of embracing the situation it seems to be overwhelming me. All of the symptoms you mentioned are there: Lack of sleep, headaches, low motivation, the inability to do the hours I used to. This is my family business. I don’t what to do to get myself out of this funk.