In another related topic, I said for motivation I usually focus on the why. You can see a longer form of my response in the original thread:
As for time management, I find it easiest to reserve or schedule a regular time to do something, ideally every day but at least more frequently than once a week. Explicitly setting aside a time that I always use for working on the game allows me to enjoy the other important parts of my life with less conflict. I would like to say that it entirely eliminates the feeling that I should always be working, but unfortunately as an indie who doesn’t make very much money it is sometimes very hard to not have this feeling.
I did prefer this arrangement when I had a full-time job too. Working a little bit more often (ie. most weekday nights) instead of a lot less often (ie. every Saturday) makes it easier to remember the context of what I was working on and makes it more likely that I just do the thing automatically as a habit – instead of having to spend willpower motivating myself into starting it back up again.
That’s what works for me anyway, your mileage may vary.