Dedicate at least one night a week to a project. When you get home from the day job, you start work on the project, and you keep at it for at least 6 hours. Make sure this night becomes a sacred obligation, you don't skip it for anything but weddings/funerals.
This helps ensure the project progresses on a weekly basis. It protects the time from family/friends/spouses who may not understand or accept that you are busy at random times, but can understand a scheduled obligation.
caveats: One night a week is usually too slow for any project, so don't use this as a crutch, you should still pour hours into whatever you do throughout the week out of passion - this is a safety valve for busy or passionless times.
It is a lot easier to pull this off with a group of like-minded people, try to get a couple other people (even remote) to join you in the endeavor.
Good luck!