Dear Satabdee,
Firstly, don't take stress. It is a common thing among students.
In order to concentrate on your studies you goal should be clear. You should be motivated and determined to acheive your aim.
If you want you can make your important time table it will help you to complete your syllabus and you can get proper time for revision as well.
If you want you can set your daily and weekly targets.
You can also make your important notes it will help you to concentrate and will help you at the time of revision.
It is very important to clear your doubts and analyse your preparation level by giving test.
If you want you can also join study group it will help you to concentrate and you will also get to know your competition.
It is your career and very important time to build your future. Don't waste your time utilise it to get better results.
All the Best!!
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