If worked hard and studied sincerely then you can clear JEE Mains Entrance Examination. 

Prepare a timetable for each day. Fit in hours for every subject each day. This is because every subject is important. Study the chapters you find difficult in the morning. Take 2-4 mins break between 1-2 hours of study. In break close eyes and meditate. It increases a person's concentration. 

Start studying from NCERT textbooks of 11th and 12th standards of Physics, Mathematics and Chemistry. 

NCERT textbooks are helpful for entrance preparation. There are many other reference books available for JEE Exam. I would suggest you not to refer 5-7 books for a subject as it will only create confusion. 

Refer 2-3 books for a subject and study them thoroughly. 

Solve Multiple Choice Questions everyday based on the chapter you finish on that particular day. 

Solve previous year questions and give mock tests. Analyse mock tests and see where silly mistakes are happening and avoid them in final examination. 

Prepare notes of chapters. Also prepare different notes which will contain formulas which can be referred before entrance examination. 

Do not take stress as it will only lead to other problems. 

If you still have any queries feel free to ask in the comment section down below.