One of the reasons why we dream at night is to consolidate the learnings of the day, it makes them become more instinctual. Every night you dream after playing that day it is incorporating your play for the day into your unconscious mind, forming “new files” as an old friend used to refer to them.
Studies have shown that you can not only maintain muscle memory developed through physical practice, but also maintain and even further develop muscle memory through closing your eyes, meditating, and visualizing yourself playing. It can also be done through watching video of yourself and others playing. This is done through “mirror neurons” which help us watch others and be able to learn, copy, and repeat what they are doing, it’s how infant children learn through watching their parents.
A good thing to do is to video yourself while playing at peak level and to watch that once or preferably several times prior to going to sleep, and also first thing after you awake to reaffirm it. Doing so just prior to sleep is like creating a “program” for your unconscious to work on as you sleep/dream. It’s common knowledge that your dreams are generally about the last things you do, watch or think about prior to going to sleep.