At first you will have a few problem if you have done 10th from CBSE, if you are from ICSE then also you will have a few problems but you will recover much easier than CBSE students.
Your only nightmare will be physics because its entirely different syllabus from 10th and you will have to remember much bigger formulas, much lengthy and conceptual derivations,and then also there is a possibility than you will find it tough to solve questions!! But you dont need to panic because when you are done with part-1 of class 11th physics,rest all will be very easier, you will find part-2 and even class 12th physics quite easy.
Rest all subjects be it maths,chemistry you will be good at it! Just remember than you need to have some patience for a few months,DO NOT PANIC as you will find some ‘out of the space questions’ from your coaching packages and ofcorse WORK HARD!