Mornings go well, evenings go badly. Is that a real thing?

There is a real difference and there is also a confound, and I would be careful about which one you have. Mornings for most people mean rested, unhurried and nothing else on the mind. Evenings mean tired, a day behind you and half an eye on the time. That is not the clock, it is everything the clock is standing in for.

Same pattern here and I tested it in the least scientific way possible by trying a Saturday afternoon, which is neither. Went like a morning. Which suggests Kate is right and it is the tiredness rather than the hour.

Whatever the cause, the sensible response is to stop fighting it. If mornings work, do mornings. People spend a lot of effort trying to make the difficult version work when the easy version was available the whole time.

One correction to the general enthusiasm for mornings. Some people are markedly more sensitive first thing, which makes control harder rather than easier, and they will read this thread and think they are doing it wrong. There is no universal good time. There is your good time.