I'm thinking of passing off my classmate's flawless work as my own.
Why not rely on your own skills instead?
I know I'm taking a big risk, but I feel there is no other way out.
It's wrong and a bad idea to steal someone else's completed assignment. You will get caught if you do this and will have severe consequences with your teacher and your school. Additionally, you will only prevent yourself from demonstrating your own ability.
I really can't stand the thought of having to do my own homework anymore. It's driving me crazy.
If you're having trouble focusing, why not try asking your teacher for help or hiring a tutor? There's lots of patient people who want to see you succeed, so please don't cheat! You are very capable and don't need to steal, you just need to find that little switch on you.