The truth is a few years ago I tried my first MMO, a bunch of my friends joined me.
we played mostly after work and weekends. Then slowly everyone quit.
I was about to quit also when I met someone, this person was an RP player.
I was told think of yourself as the character. I tried.
Unfortunately I have a neuro-muscular disorder that had not presented until that time.
I suffered 3 strokes while in character they were minor strokes so I remained functional for the most part, the result was I lost myself, I was actually surprised by the mirror. Now I don’t mean I totally became someone else, only that while playing I would lose the real world and not snap out of it right away when I left the game. Also I lost almost all of the trivial parts of my memory as in I couldn’t remember minor things.
My work became overwhelming, things that were simple yesterday became impossible today.
I recovered partially over time, but I still have trouble remembering. My muscles have degenerated.
But I can still walk just not far, so I consider myself lucky.
So now RP to me is just a puppet-master I keep myself removed from whatever I do in game.
Sorry that is probably too much information. but you asked.
edit: it was a year and a half before the doctors figured out what was going on, my family noticed something was wrong straight away, but it was still a year and a half until the problem was diagnosed by a muscle biopsy.