Painting from memory is a good way to think through and analyze what you just saw. Like reading a book, then describing it in your own words, memorizing forces me to view the scene differently, looking only for the important big stuff that I can remember and translate into value and temperature. It’s easier to remember and compose large, flat patterns of dark and light and the results are different from painting from life and a lot different than painting from a photograph. I’m forced to push value and color to make a statement from what I remember. I can’t use detail because I won’t remember any.
Painting from memory works best for me when the lighting is more dramatic. Sunsets are a good practice. They’re too short to paint from life and photographs never do them justice. The other benefit is that using your memory helps prevent altzhiemer’s, so use it while you have it.