There are a few tactics I use to stay on track! These include:
Only studying for 1 hour max- I find that if I study for longer than 1 hour chunks (sometimes even 40 minutes), I start procrastinating and checking my phone constantly.
Setting goals for each hour- When I set a goal for every hour of study, I feel motivated to achieve that goal. For example, if my goal is to finish revising chapter 2, I will not procrastinate until I know that I will finish the chapter in time.
Setting big goals for each hour- When I set very achievable goals (e.g.: revise 1 chapter), I tend to procrastinate because I know that I can easily achieve them in and hour. Instead, I try set optimistic goals for myself (e.g.: revise 2/3 chapters) in an hour. By doing this, I make sure that I don't procrastinate.
Reminding myself why I want to reach the goal- If I don't have a reason for achieving my goal, why do it?! I usually want to finish the work so that I can take the next day off, or have a super long break that day.
Of course there are days when even these don't work, but for the majority of the time they do A okay!