#1 Set aside time to work This is the important part, you can't "work when you're inspired". Set aside the 2-3 hours you need per day. At the time I had a full-time job and the baby was born. My partner at the time was a stay-at-home-mom, which helped a lot. But I had duties to be with the baby in the evenings -- feedings, etc. I watched a movie or series with my partner after the baby was sleeping, THEN I went to work when my partner was sleeping.
#2 Constraints are important Because of the minimal amount of time (few hours per day) you have to spend it wisely. In this case, I had a strong to-do list with few distractions. I would work on that list and try to finish a few items (completely) every night.
#3 No distractions No social media was consumed. No YouTube, no instagram, no twitter, tv off. Back in those days these services were just starting anyway, so things were kind of "new".
#4 Motivations Biggest motivator was my family. Living in New York City was not easy in a nice apartment and a family to support. I knew my side project HAD to work and it DID because I had NO choice. Even with an almost 6 figure job, it would not have been able to do everything, even in 2004.
At some point, you have to balance out things. You CAN't spend all your time with your family.
And you can't spend all your time with your job.
You have to have some time for each one. And where people fail badly, is when they spend quantity instead of quality time with kids or work.
Believe me, its best to spend less, but QUALITY time with your kids, rather then a whole lot of random time.
Your mileage will not vary.