I m not able to concentrate on my studies. I am preparing for competitive exams that require at least 10 to 12 hours of study daily. I feel lazy n sleepy n keep on yawning while studying even after I take 8 hrs of sleep. I can't sit for long to study. I want to increase my capacity of sitting for long hours to study as well as my concentration power. I want to focus as much as possible because this is the crucial time to build my career. please also suggest diet. Exercise. Yoga. Whatever that may help in my case.