There are few constant rules to writing which apply to everyone. But there are some. One is to realize that what you are doing (and may have been doing for years and with which you are very comfortable) is no longer working. It is difficult to alter a comfortable routine of long-standing, but, if it is broke . . .
I have started a different writing regimen. Well, starting is an exaggeration as I have been doing it for six weeks. I guess it's going to stick.I was having trouble getting started in the day. I didn't feel bored, and I had no trouble once I did start writing. However there seemed to be an initial tiredness of some sort. Since I know I do get mentally tired from the writing, I decided to take more time away from it. When all was said and done, the conventional weekend seemed the best. So, I now write five days a week, but I am writing two pages a day instead of one. The tiredness has not returned, and the two pages are not difficult. And I am writing longer each day than I used to. I am apparently being shown how to allot both my creative and physical energy. With my writing-time shaped into a different configuration, perhaps I'll squeeze out a couple of additional novels. Maybe even a memoir.