Why focus 100% on studying? studies are part of your life, Not your life. What ever other suggests you, its you who need to figure out what works for you.
So , sit down and grab a pen and a paper and write down what are your thoughts while you are studying and are you able to concentrate on studies or day dreaming about any other things.
Write down the difference between studying your interesting subjects / topics VS Not interested subjects / Topics. If you have noted that while studying your interesting subjects / topics you are unable to focus then its may be because you lack focusing and you need to think how to improve your focus , In this case you can concentrate on writing down / chanting your goals and how important it is to study the syllabus and get good marks , And try other methods which are suggested by others.
If you are able to concentrate while studying interesting subjects / topics and unable to focus on other subjects/topics then it may be because of you have not understood those subjects or something else. In this case consult your teacher or some once who has enough knowledge to explain you the subjects / topics easily so that you can understand them.