That may just be misplaced energy. If you can't study but you can sit there practicing guitar or working on a hobby coding project for hours, you are certainly

That may just be misplaced energy. If you can't study but you can sit there practicing guitar or working on a hobby coding project for hours, you are certainly capable in a physical sense. But your mind cannot say "I will do my homework with identical enthusiasm to my guitar practice" and just have it happen. That is where the mythical aspect of willpower manifests and people do all sorts of things to try to make it work like that, but most people, I think, end up finding a substance to use that blunts their thinking in a particular way that helps them stay on task. That could be caffeine, or alcohol, or pot, or Adderall. Other people try to build elaborate social obligations with study groups and use of office hours. But the biggest success tends to be from getting the intrinsic motivations in place, the "I want to know what happens next" factor and those are never easy to find. Sometimes you just have to start from zero and do something very simple and low energy like washing dishes before you can access a higher level of concentration, and then quickly use that moment of concentration to make a breakthrough.