And if you still want to do a side project then work on it and market it for maximum of an hour every day but for, at least, a year before starting a next project.
Ack. I had this thing where I would feel guilty in the evenings for not working on side projects.
I was getting up at 6am and doing the dad thing for my two kids getting them fed and ready for school. Walking the dog at 8am and then working from 9am to 5-6pm. Then I would do the dad thing again, until the kids went to bed at 7-8 pm. Spend an hour or so with my wife and then stare bleary eyed at a load of terminals and code until 11-12pm, feeling guilty that I was not the next greatest individual creating cutting edge tech.
Now I have a no work policy in the evening. I still spend time on learning new tech, but I do this for short periods during the working week / hours.
Do what you enjoy in the evenings.
And if you still want to do a side project then work on it and market it for maximum of an hour every day but for, at least, a year before starting a next project.