Consider doing less. If you are working a full time job, then depending on exactly how serious you are, 3 learning projects is likely overkill. (But I tend to do the same thing myself.)
Pick the resources you'll use in advance. I've generally had a negative opinion about video lectures, preferring books, but I've somewhat changed my thoughts lately. In particular it's nice to be able to follow a course as it was taught at a serious university, with a syllabus and schedule all laid out for you.
Set a weekly schedule in advance. Something like, M/F I'll watch a data science lecture and Tu/Th I'll do art. Whatever. Include a planned endpoint: by this date I will be finished with the 9 chapters of this book I plan to cover.
Each evening, write a brief journal entry about what you accomplished that day. Also write out a schedule for the next day. I like to put at the top of my daily schedule a list of the major tasks I want to accomplish that day, and then also a couple "extras", which are things I can work on if I turn out to have extra time. The extras can be large or small, but it's nice if you have a small one because you can cram it in wherever you have free time. Even something like "Problem 12.3 from this textbook, which I couldn't figure out last week". If you randomly turn out to have 10 minutes free, well pull out your notebook and think about that problem for 10 minutes.
(By the way, I know an eminent mathematician, one of the few who has done serious work in multiple fields, who says one of the attributes that has helped him the most is his ability to efficiently context switch and get serious work done throughout the day. If he has a random 18 minutes free, he is going to make 18 minutes' worth of progress on a research project.)
Jerry Seinfeld's "Don't break the chain" idea is nice.
As far as tips for learning: engage and fight with the material, do projects incorporating what you're learning, make connections to other things you know. Incorporate reviews of earlier chapters/lectures, rather than just continually charging ahead. There's a bunch of resources for how to learn (see for instance those mentioned in this HN thread [1]), which I think are good ideas, although honestly I have only haphazardly incorporated these techniques.
A major thing I haven't really figured out is maintaining / reviewing. I can personally attest to the fact that it is literally possible to be an expert in a subject one day, and less than a year later struggle to remember elementary knowledge that every beginning student learns. Maybe there is no perfect solution to this problem, but maybe it's possible to come up with some review schedule that helps more than "every now and then I randomly go back and look at a book I once read."