Largely this is a class thing - writers tend to be cosseted little middle-class kiddies who think that the world owes them a royalty cheque. But just doing it - being in your room for years on end locked in your head alone with invented ghosts - it weakens and softens the body. And I know I can't just live in my head.
I trained to be a priest - started to. I went to seminary school when I was 11. I wanted to be a priest but when they told me I could never have sex not even on my birthday I changed my mind.