Yes I get the point.
For every subject I want to study I start by having a look at some books' timetable. It gives me the key points to understand about that very subject like a sort of study guide. Small parts that I can learn in an hour or less. I have a schedule for the week, with multiple points to learn. It's like a time constraint as others mentioned.
You also can try to find some (very) short (and interesting) projects. I think short is important as you seem to move very quickly to the next subject. Maybe it could help to keep focus on one topic at the time and keep you motivated. It's a good idea that you add the time constraint as other suggested you like sprints / user stories.
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