Let's say for a second that your sister is indeed smarter than you. It's wonderful for her that she's bright and still says very little about you.
I agree with another poster that your parents expectations are unfair and damaging to you. It could also be that you're seeing your parents actions unfairly. Maybe they're abusive, maybe they're scared for you and only have your sister to compare to in their experience.
Either way I would urge you to move out when you reasonably and safely can so that you can start to build your own life by your priorities and expectations.
It's my opinion that people don't have any clue who they are until they have the independence to discover themselves.
Your parents are supposed to help you get the tools to do that and exist in the world.
Maybe they're doing that poorly, maybe they did well enough, but you seem to no longer be effectively growing while living there... so what's next?
Any attempt at self-improvement is not pathetic. My phone suggested self-forgiveness, which also is key here.
You are trying to be more aware and less impulsive. The key here is mindfulness, not that it's easy to attain/achieve.
I said self-forgiveness because beating yourself up for your perceived failures will also hold you back.
Failure is key to success.
I've made a little progress toward changing my internal monolog, and it has served me well. Be nicer to yourself and laugh off your failures lest the memory of them become baggage.
My dad is a Buddhist. I never got good at meditation, but I recognize its value.
But mainly, be kinder to yourself. Perfection was never an option, so why would you expect it from yourself?
Relax. Breathe. You'll figure things out, whether or not you achieve these goals.
I loved that book!