First of all, congratulations on passing 12th!
A bit of panic after completing high school is quite legitimate. This is the time, after all, when you'll be facing the real world. I know that half of the panic induced in you is because of societal and parental pressure.
Now that you have completed one phase of your education/career/life, the world is looking at you with a set of expectations. Please know that you are in no way obliged to fulfill all these expectations. Not even those of your parents.
What you need to do right now is to stop thinking as your parents' son or daughter or as a product of society and educational system. You need to start thinking as an individual who is only responsible for his/her own dreams and decisions.
It's okay if you are a science student and end being a writer or a painter. It's also okay if you couldn't be an IAS officer in future. And don't worry if your friends land better courses than you or better-paid jobs. Competition is just one part of life and shouldn't become the standard of your happiness as long as your career is concerned.
So relax, take a deep breath, explore all the options that you have before you. If you want, take a year off and pursue some of your hobby or passion until you make sense of your life, future, and career.
All the best!