I sometimes find it helps to make kind of like a 'to do' list, but make one for short term things, e.g. practical prep work, or an essay, that needs to be done for that week, and a more long-term list with things like all the lectures you want to write up, and subject areas you want to revisit at some point. Then you know exactly what needs doing and can see where your priorities lie and what needs to be done first, so you can start with that. You can then tick off all the things as you do them. Also, just seeing how much you have to do, on paper, can be good to motivate you to actually start doing your work and working through your list of tasks.
Also, if you have a lecture/session timetable from uni which has when your lectures and small group sessions etc. are scheduled, you can fill in the gaps where you have breaks with what you want to get done at that point, e.g. 2-3pm blank space on schedule- you could write in 'write up lecture 18 of module x' and try to get that done in the time, instead of just wasting time trying to think what needs doing.