I am more productive than before I had kids because time is very limited I don't lie to myself anymore. Either I'm going to sit down and work on a side project or not. No more sitting in front of a computer and clicking around while not doing anything.
Prioritize cashflow and don't slack off.
If you're early in your career, I wouldn't sweat it. Take your time. Work on side projects when you're feeling inspired to, don't force it. As your skills progress, so too will the impact of each minute you put into a project.