Reaching for "sufficient enough"

I've had a very crappy 8 weeks or so. One teacher told me, earlier in the year, that at some point you're going to hate yourself because you're not going to think you're doing a good job at all. I felt like this last semester, and understandably so, I was new to the job. But I've been teaching now for six months and I still feel that way. I've felt pretty ineffective and useless for most of the term. And what's sad is that I can see and relive positive moments that I've had in different classes this term, but they don't make me any happier or motivate me at all because they were so rare and surrounded by many more unhappy moments.

So besides sleeping and tearing up every now and then I've been thinking. Why exactly do I feel so useless? And I realized it's because I expected so much. I started out last summer making sure to have few to no expectations. Something happened along the way and I think I started expecting just about everything. I expected things to go as planned. I expected students to review the work at home. I expected to spend less time grading papers since I'd been doing it for half a year already. I expected my students to be somewhat civil in the classroom. I expected to be a better teacher than what I am now. I expected too much and didn't even know I was doing it.
In the back of my mind I keep on trying to be this sort of ideal teacher. The teacher that gets students their work in a timely manner, that does most of the things asked of her by the school administration, and that has time to help students individually, both in class and outside of class. A teacher that knows what she's doing. But sometimes I feel like I have no clue what's really going on. And I'm trying to work with this feeling of confusion and still get to this ideal teacher. I'm trying to pretend I'm not confused because I have other, slightly more immediate things to deal with. And I'm trying to walk in a straight line and maybe hold a couple things as I go. But it's not working and hasn't been. So with each step I take, to the right, then the left, then the right again, I'm still trying to walk straight and I'm still thinking of getting to the ideal teacher that's waiting for me, but I'm getting quite frustrated because I can't get my feet to do what my mind wants. And the mind.. the mind is supposed to control your body's movements. If the mind says walk straight, the body should walk straight. And if my mind says be a good teacher, then i should be a good teacher. But this is not happening. I'm still walking to the right and to the left and I'm still not where I want to be as a teacher.
Anyways. So that day that I was thinking, I also thought, "What would've happened if i came in here trying to be sufficient enough? If i had no hopes for greatness in any part of my teaching?" If I didn't have this idea of me as an "ideal teacher," it wouldn't matter that I was walking to the right and to the left. If that didn't matter, then I wouldn't be so unsatisfied and frustrated right now. My problem has been this ideal and my expectations. If i threw them all out the window, I would probably have fewer teaching nightmares, would have more time to actually eat a lunch... I could probably throw my bottles of Advil and DayQuil in the garbage...
But then i thought "Of course you can't do that. You'd be no different from too many others and that's why you're here."... yeah yeah i know. And of course, this was just one thought I had for a couple seconds a lil' while ago. I'll keep on doing what I'm supposed to as best as i can.

This is really beginning to take the life out of me. I'm just trying to find a solution, because you can't do anything with a dead teacher.