If a subject feels like a wall, find one brick you can pull out. Then another.

A subject feels impossible when you meet it all at once, as a single solid thing you either get or do not. It is never really that. It is a lot of small pieces stacked up, and one of them is always loose enough to work on today. Pull that one out and the wall stops being a wall and turns into a list.

Take the subject that is beating you and find the smallest piece you could understand by tonight: one definition, one worked example, one step of the method. Do that, then pick the next loose piece tomorrow.