[AnimalMuppet]

This isn't assembly line work. If your brain is too tired, it doesn't matter if your butt is in the seat, you're still not going to be effective. In fact, you may be negatively effective - it may take time to undo the damage that you are doing to the code base.

One of the rules of XP is "Quit when you're tired." XP is all about going as fast as you can. The fastest you can go involves quitting when you're tired. Stay longer, and your productivity goes down, not just that day but the next, and maybe even the day or two after that.

It sounds like you're working at a place that doesn't understand that. (It also sounds like you're working at a place that is somewhat exploitative.) To get a reasonable life, you may have to leave for somewhere else.

Unfortunately, right at this moment is perhaps not the greatest time to be changing jobs. If your current job is stable and unaffected by Corona, you probably should think twice before you leave - unless you're pretty sure that the new job is also stable and won't be affected by Corona.