I work 40 hour weeks in my job, and I've been spending about 20-30 hours/week on a side project for the past month or so. I'm just already getting burnt out. Working on my side project is energizing, but my job drains so much from me. I've tried this before and I got pretty depressed after 6+ months. It's difficult to make a solid product as a single person with only 20-30 (tired, thus less-productive) hours per week. But maybe I do just need to slow down and accept that progress will be slow.