I believe structure is important, and that the teacher must have control to bring order and meaning to the classroom.
Frustration in any job is not pleasant, but in teaching it can be harmful and cause us to not do our best. I would suggest that staff development is in order. A workshop could be very helpful and give you back the positive attitude and enthusiasm you want. Different parts of the country have different speakers and conferences. Ask around to find out who the popular speakers are and select one who matches your academic area or middle school student population.
You are working with children who are at an important point in their lives developmentally. You can be very powerful in influencing them. Don't burn out and succumb to your frustrations.