Sometimes, what you think I think also. It’s not come for your laziness, inattentiveness is one of the reasons. Keep a actual procedure during your study time.
No1.  Keep healthy your mind. Yoga and exercise are good.
No2.  Be active during study time. Don’t divert your mind to others thing.
No3.  Try varitiness. A child’s education is isolated due to lack of varitiness. Try new concept, chapter, online education, etc.