Firstly, congratulations on finishing your 12th exams and JEE. I think you still have a chance. Because you will have a second chance to attempt JEE. It is better to wait and see if you couldn't make it in the second attempt also. If you miss it very closely and if you wanted to study only in NIT's or IIT's then you can think of dropping. But as far as I heard from people it is actually not a very good idea to go for longterm in MPC. It is like wasting your one year. Even if you donot study in NIT or IIT, you can still manage to get a decent job if you work it out during your graduation.

I finally suggest that if you miss JEE merely then you can think od dropping out only after your second attempt. If not donot waste your time. Gook luck for your second attempt of JEE.