When you study, you should be serious about the study and you have to concentrate on the studies, then only you will learn the subject. Even though you are having an open book in your hands and your eyes are seeing them but if you are not applying your mind and if you are not serious to understand the subject nothing will get into your mind.
This is the main difference between the winner and loser. A loser will not be serious about the task in his hands. He can't prioritise his works. Half here and half there he will be doing. But a winner will think about the task on hand only.
Guru Drona asked his students Pandavas and Kauravas to shoot a bird on the tree. Before shooting he asked each one of them, what they are seeing. Only Arjuna answered that he is seeing only the eye of the bird which he has to shoot. All others replied differently. Then Drona said that Arjuna is only having the required level of concentration and that is why he will be the best shooter.