A one-hundred-thousand-word novel might take a year or several years, and then you just come to 'The End' one day. But it takes hundreds of days to get to 'The End.' As a writer, you have to put in those hundreds of days.
Completing any writing project, particularly a novel, is a daunting prospect. Many people become frozen by the prospect. Others keep waiting for the right time. Some wait for the spark of inspiration. Even experienced writers find it is easier to do anything other than actually write.
The most important thing is readers. I've got a huge Twitter following, but I don't really think it sells books; I don't think a huge Facebook following sells books - although these things aren't bad, of course.