As is evident from your marks secured in 10 th class to the extent of 76 percent indicates that you are above the average. Moreover, you had been recipient of distinction - degree in Science, Mathematics and English in the same examination. By combining these two factors together, I am of the impression that you can repeat such outstanding performance even in class 10+2 Board - examination.
The most important factor to excel well in the examination is to come out of the negativity with which you are currently engrossed and you can change your mind frame by going through the life - history of the great men and in that way, you would be able to shed your existing negative emotions and would be charged with the positive ones'. The following points would help you in the preparation of the examination systematically.
1) You must restrict to a few books for each subject for reference - purpose in order to avoid confusion.
2) Sample - papers in each subjects for at least five years must be practiced to have clear grasp of the pattern of the examination. Assess the time of your completion of answers and see if you have completed the same within the scheduled time frame.
3) It would be best to stick to NCERT text - books since all the relevant points have been incorporated in the same. Any doubt arising out of your studies should be sorted out with your teachers.
4) Never compare yourself with others in respect of your preparation because such comparison may set in negativity.
5) You must be consistent in your studies. Allocate sufficient time for revision.
6) As far possible take nutritive diet and fruits such as Apples, Bananas, Dry fruits especially walnuts, cashews in a little quantity should be included in order to get healthy nutrient supplementation. A sound sleep for a minimum period of eight hours is essential to lessen your stress.