As I said before, I'm rereading one of Jack Bickham's books on writing. I think I have all of his books, but this is one I particularly like. The 38 Most Common Fiction Writing Mistakes is pithy and easy to read. The chapters are two to three pages long. In an early chapter, Mr. Bickham said: "The writing of fiction is very deceptive. ...it looks easy until you try it."
As a writer with more than a few manuscripts, published and unpublished, behind me, I know this truth in every cell of my brain. This is why I always encourage those who tell me they're going to write a book when they have the time. I tell them to go for it. They may succeed.
If they've been particularly condescending in their assumption that free time is all that is needed to write successfully (of course, I'm thinking of one particular individual here), I stand a good chance of being greatly amused when I bump into them in the future. I've yet to hear anything but hemming and hawing from those who've actually tried to turn their idea into a book.
More is required than leisure time to successfully write. If you want to write, you must be willing to work hard. Writing is hard on the anatomy, the brain, and the emotions. I think it was Earl Nightingale who said: "There are no bargains at the counter of success. You must pay full price."