For a while last year, I did just accept it and stay up late until I felt more tired, usually around 1:30am. We were both working from home and I'd sleep in a little bit (which is also getting harder in my late 30s). This wasn't perfect but it was better. But now my wife is back at the office and is out of bed before 8am, which wakes me up and usually I can't get back to sleep easily so I've been struggling since.

I've tried exercise both during the day and the evening in case it's a physical thing, but it either doesn't help or makes it worse. Sometimes my active brain state amplifies physical aches and pains and itches and it just runs away from me and is very distracting.

I think what might really be missing is a sense of closure or achievement. A lot of things in life can give gratification without meaning, but the days I do something like finish fixing the shower or putting up shelves, it does seem a bit easier to switch off at night. Cooking is the closest I get most days.