Planning
Break assignments into concrete sessions. Set a due date and priority for each task, check things off as you finish them, and let the planner sort everything so the most urgent work always floats to the top.
Using it well
Most study plans fail because they are built around time ("study biology 6 to 8") rather than tasks ("finish problems 1 to 15 in section 4.2"). A time-based plan has no way of being finished early and no way of telling you how far behind you are. A task-based plan does both. Enter tasks that are specific enough that you would know when they are done, and small enough to complete in one sitting.
The planner is also the simplest way to run a review schedule. When you learn a new topic, enter its reviews as separate tasks dated one, three, seven, and fourteen days out. Each morning, the list shows what is due. The spaced repetition guide explains why those intervals, and the exam plan shows how to lay out the fortnight before a test so the hard topics come first instead of last.
Be realistic about capacity. If you can genuinely do four focused blocks of work on a school night, plan four, not eight. A plan that gets abandoned on Tuesday because it was impossible teaches you to ignore plans. One that gets finished teaches you to trust them. If you are not sure what your capacity is, run the Pomodoro Timer for a week and count.