Not my own answer, but here's a fun story from the always-fascinating Robert Sapolsky (renowned neuroscientist, author, and a beloved teacher) telling us about how he got into writing[1]. (NB: it's a transcript of a verbal conversation, not a written response; hence the "Sos" and the slight meandering. I found the full transcript to be interesting.)
Interviewer: Where did that [ability to write] come from? I mean, did you begin writing for school – all of a sudden in third grade you got this delight?"
Sapolsky: Naaa...
Sapolsky: [...] I was OK with writing, and throughout college I didn't have a writer's block. So I had friends who would pull their hair out over it, and that was sort the central organizing emphasis of their life, and I never had a writer’s block. It was something that I was OK at, but nothing I took any great pleasure in. I never took a literature class in college, or any English course or anything.
And I was not particularly into writing, and it was not until after I finished college—right after, a week after graduation—I went off to Africa for a year and a half to begin to get my field work started, which I have been doing ever since for twenty-five years and it was fairly isolated site, where a lot of the time I was by myself. I would go 8 to 10 hours a day without speaking to anyone, I would get a mail drop about once every two weeks or so, there was no electricity, there was no radio, there was no anything, and I suddenly got unbelievably, frantically dependent on mail. So as a result you wind up sending letters to every human that you have known in your life in hopes that they would write back to you.
So what would happen is, all I could afford at the time were like these one-page aerogram things that you could sort of get in these big stacks, and something vaguely interesting would happen every couple of days or so. So you would write to somebody about it, and then you would write to the next person about it, and you would realize that before the end of the day, you had just written 25 versions of it, each of which was a page and a half long. [...]
Interviewer: Where did that [ability to write] come from? I mean, did you begin writing for school – all of a sudden in third grade you got this delight?"
Sapolsky: Naaa...
Sapolsky: [...] I was OK with writing, and throughout college I didn't have a writer's block. So I had friends who would pull their hair out over it, and that was sort the central organizing emphasis of their life, and I never had a writer’s block. It was something that I was OK at, but nothing I took any great pleasure in. I never took a literature class in college, or any English course or anything.
And I was not particularly into writing, and it was not until after I finished college—right after, a week after graduation—I went off to Africa for a year and a half to begin to get my field work started, which I have been doing ever since for twenty-five years and it was fairly isolated site, where a lot of the time I was by myself. I would go 8 to 10 hours a day without speaking to anyone, I would get a mail drop about once every two weeks or so, there was no electricity, there was no radio, there was no anything, and I suddenly got unbelievably, frantically dependent on mail. So as a result you wind up sending letters to every human that you have known in your life in hopes that they would write back to you.
So what would happen is, all I could afford at the time were like these one-page aerogram things that you could sort of get in these big stacks, and something vaguely interesting would happen every couple of days or so. So you would write to somebody about it, and then you would write to the next person about it, and you would realize that before the end of the day, you had just written 25 versions of it, each of which was a page and a half long. [...]
[1] http://web.stanford.edu/group/howiwrite/Transcripts/Sapolsky...