I started to write a book about 20 some years ago, when I had access to a computer at work and was underemployed. It went quite well and the one person I trusted to give me an honest opinion was very enthusiastic. I then left that company and went through a maelstrom of change for the next few years and then, when I retired, pulled it up and had a look at it.
Unfortunately, by then my arthritis meant that I cannot type well enough to do as much as I'd like and is necessary to do any more.
What I do use it for, however, is to put myself to sleep. I have written the entire book in my head and then gone back and redeveloped sections ad nauseaum. I turn out the light, snuggle down and think to myself "Now, which bit am I going to go over tonight?"
It's become my favourite way to go to sleep!