Jobs give structure. Especially the 9-5 variety. Times are clearly defined. Get up at time X. Lunch at time Y. Leave work at time Z. Free time until you must get up again at X.
I’ve never been much for that kind of structure, though. I find that there are too many times when the mind wanders and I’m unproductive. Likewise sometimes there’s not enough work to fill the day or there’s too much work to fill the day. I’ve found that I’m more productive in pursuing my own schedule.
Of course there are times when I’m definitely procrastinating. But I’ve found in my writing schedule that I can (when there are not ten billion other things happening) maintain a strict discipline even among various activities.
Over the course of the past year, I’ve engaged in half a dozen different projects nearly simultaneously and maintained my other job as well. I’ve also had times when I needed to finish on deadlines, too, especially with multiple projects. I think that I’m up for the challenges of a more independent structure.