i am in 12th grade. i want to do something big and different in my life. and i know i can't do that much. i feel like i am overestimating myself. i know i am a average but my dreams are simply too high.

To achieve something great you have to work smart and hard. You may be overestimating yourself or here is also a possibility that you are underestimating yourself. I would say if you have a idea do that and develop skills. Make yourself outstanding. Everything is possible if we are smart enough to solve all those problems which lead us to failure.

Keep trying.

All the best for your future endeavors!