Study in the same place every time. This mentally sets you up that this is time for studying and nothing else.
Don't do it where you do something else regularly, for example, do not study in bed where you sleep. This would cause you to think of sleeping and not studying.

Try reading the Bible and ask God to give you the wisdom and patience to study well.
Also say the Divine Mercy Novena every day at three o'clock.

try to drink a glass of milk you will feel calm .i advice you to stop stading at that when you come back you will feel more better and more concentrated