Part of it is social and general anxiety. I'm afraid of putting myself out there, having my ideas and implementations judged, and finding both coworkers and customers.

Part of it is having trouble focusing on a single idea. Finding the right partner would help here: see #1.

Part of it is fluctuating levels of depression sapping my motivation outside, and sometimes inside, work. I have been fighting this for almost a decade. At one point several years ago the mere thought of doing things outside of work so reinforced how miserable I was in my day job that I couldn't get anything done.

I'm slowly working through my barriers. My most recent dip into the job market has demonstrated that the only way I am going to get the job I want where I want it is to make it myself, so I have renewed motivation to get moving.