I'm just.....done. I am so done with being a teacher. I give up.
Why are you so frustrated with teaching?
I've walked through two decades in a job I don't even like. I think I deserve a better life.
Teaching is a difficult job and it is not for everyone. If you no longer enjoy teaching, then your students will not be getting the instructor that they deserve. It's perfectly acceptable for you to transition into a different, more fulfilling career as both you and the students at your school will be better off.
I know. You're right. I am so tired, I'm just done.
I'm sorry that your job has come to be such a source of frustration for you, but it's good that you are ready to try something new.  Hopefully you can finish out the school year, and then use the summer to transition into something that is a better fit for you.