I’m beating myself up over not being a good enough teacher!

I don’t get my grading done quickly enough!  I’m not challenging the kids enough!  I’m not teaching the right things rigorously enough!  I’m not e-mailing parents enough!  I’m asking too much of the kids!  I’m expecting too much without enough reinforcement!  I’m a giant time-wasting asshole who shouldn’t be allowed in the classroom!

But also the kids aren’t smart enough!  The parents aren’t supportive enough!  I’m not paid enough!  I don’t have enough time!  I never wanted to be a teacher, anyway!  Everything sucks forever augggggghhhhhh!!!

How do you get out of the negativity spiral?  How do you find balance and still feel like you are doing a good job?