I start my weekend on Friday night - usually I go out with friends to a bar or a night club. On Saturdays and Sundays I do whatever I feel like doing:
and almost every weekend I work on my side projects. It's like my hobby and I get used to it for a long time now. Some weekends I code for 1 hour, some weekends I get 10-12 hours streaks, it's different every time. I don't give myself deadlines, roadmaps or schedules - I start coding and see where it gets me. This means that when I feel exhausted, unmotivated or onerous I can stop whenever I want!
My rule is - do whatever and whenever you want to feel inspired and fuelled through the whole week!