I was freelancing as a teenager up until my early 20s, and I thought I was doing alright. Then I took a job at a place and learned a LOT. How to set more accurate deadlines, client interaction, how to properly hand off a project, how other successful developers are building software... a LOT.
I left that job after a year and started freelancing again but at a whole new level. I had made a ton connections at work for one, so finding a freelance project became a lot easier from that alone.