Nervousness. What should i do?

Hey, First thing to do when you want to pursue any career is to check it's basic requirements and the next thing would be to find out if there is a way for you to fit in with the requirements. Basic requirements for CDS should be readily available on net. If by physique, you mean certain expectations about physique, check if there is a way you could match it. Next step would be to make a pro & con list about the things you like and the ones you don't and mark each point in the list with a number(1-10) representing the extent to which it's important to you. It would give you certain clarity about your choice. When it comes to rigorous training, it's something which would push you hard & help you strengthen your body and mind. You need not worry about it, if you are a person comfortable with disciplined life. Finally ensure that you choose a career which is your best self-expression rather than settling for something convenient or popular. It's better to be a star at home rather than be a mediocre on stage.