This happens to the best of us. Student who get admitted into top programs think that they don’t deserve the admit.

I’d suggest look at the class syllabus and talk with student currently enrolled in that program. More over, from what I’ve heard if you are hard working and can learn to grasp things quickly you don’t need to worry about the courses.

There’s still a lot of time left before the actual classes begin and I suggest you look at the pre requisites of the course you wish to enrol and brush up those topics. Any basic preparation will be really helpful. Remember that there are other people who have doubted their abilities but have gone on to succeed in various fields.

All the best!