My conclusions (what is useful and what isn't) were always wrong and I ended up not learning anything properly, not getting a proper understanding of anything.
Please, if there is still any such option for you in your country, always choose a proper school education instead of self-learning. It is really great, when there is some leader with a proper understanding of the subject (a teacher) and others, who are having "the pain" with you (classmates), so you can see you are not "suffering" alone, and you don't start making your own conclusions (since you would see, that others are taking seriously what you wanted to call a waste of time). Classmates also help each other during the learning process.
So personally, I think a person gives up self-learning as soon as it becomes too painful / boring. The best way to overcome it is to see other people around you going through the same process, or to see somebody who you admire, who has already gone through the same process (it could be your teacher, your parent, your role model etc.). You could call that "the motivation".