I am not able to concentrate on my studies. I am not able to complete my daily task. What should I do ??

Hello,
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One can't focus on the things when they are literally busy with other work or not able to concentrate due to other issues like, fun, games, friends etc.,
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Now, if you are busy with the things in your life, then start preparation only for 1 hour in a day, as the days goes on, you will  itself increase the time for preparation, as your interest increases.
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Now, if your are getting diverted with friends, games and other things. Then, firstly make a thing clear that, there's no value for a life without education. Make a strong aim that, you will complete the syllabus in this time, no Matter what.
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Try to watch, life stories for successful person, there struggle, there hardwork, will inspire your making your goals strong.
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As you mentioned  JEE examination, the examination is not that easy to crack and make a good scoring. You should definitely work harder and complete your syllabus a month before examination