Have you made yourself a timetable? It can help by being really structured, as then you know exactly what you need to learn in a certain time period. This both makes it less daunting and more rewarding. You can concentrate on that one task. i also try and break it into pretty small chunks - revise for 30 / 40 mins, and then have 5 - 10 mins off . and then after 2 hours take a long break. this is supposed to be much more effective and makes focussing easier.
Have you also tried switching up different forms of revision? Youtube channels can be useful, platforms like Seneca Learning are really engaging and make learning super easy, and then quiz sites can be good like quizlet. Basically best to give each of these a go, and see which resonates best with you!