Don't rely solely and only on motivation, instead of that make studying a daily habit.
Create realistic goals that are achievable by you and remind yourself of them when your motivation is low.
Make a study schedule to help channelise and give a structure to your day and stick to it as much as possible.
Plan what you are going to study and break down large topics into more manageable and smaller ones.
Create a distraction-free study space where your brain can focus on the task at hand. Keep the space organised and very well placed.
Keep resources, notes and study necessities within reach, so that you do not have to interrupt your study session to search for something.
Take plenty of refreshing breaks to help you concentrate for longer, for example you can make a 25 minute study and 5 min break pattern.
Look after your physical and mental health and listen to your body, keep yourself physically and mentally fit to avoid other issues.
Make sure to get plenty of fresh air and get some exercise. They both help in refreshing the mind and make you energised again.
Reward yourself when you reach your targets as a positive aspect, this will make your brain think of performing the tasks with more effort.