I first heard "Maladaptive Daydreaming" from a reddit friend a couple months back--I looked it up right away, and I recognized a lot of the symptoms, but pretty much stopped there. I didn't want to talk to my physician about something not recognized by the DSM. However, I've recently started to take note of how its negatively affecting me.
I've been daydreaming forever it feels like;I remember realizing in grade school that I didn't have to actually pay attention to the lecture, I could instead imagine something more interesting happening. It didn't have a bad effect on my grades though, I was good enough at multi-tasking--I guess I was paying just enough attention to the teacher to still pass. (I did this all through mandatory school, as well as the few college courses I took).
Most of my daydreams start out with myself and other real people as the cast, and then later turn into original stories that I work on in hopes of being able to actually produce someday (which might just being an excuse to validate pacing and talking to myself for hours on end). As it seems some others do, I also prefer to pace and listen to music while I daydream, though I'm able to do it sitting still in silence if need be. I just think that the physical exertion and appropriate "soundtrack" helps to get into the scene better. I also think saying the lines out loud helps you find the inflection that sounds best. Without a doubt, the most interesting part of this whole ordeal, I think, is the replaying of scenes overand overand over...
There's more, but I think this is a good point to stop for right now.
While daydreaming itself isn't harmful (when done in moderation it actually is very helpful for creativity and problem solving and it can even be a healthy coping skill sometimes), once it begins to interfere with your life it becomes more of a problem.
There's tips all over the forum for dealing with it and I would definitely recommend cultivating awareness of what's happening when you're daydreaming: what are your triggers, what are your main themes, what are you trying to get out of daydreaming, etc.
Don't give up what you want most for what you want now.