I just left the following as a comment to a high school teacher's post about disillusionment, and I thought it was worth reposting.
I think one of the most important factors in me enjoying my job and feeling successful at it has been other teachers. Having other adults to talk to about my kids, my content, my lessons has been crucial to ensuring my success. And those adults have included my mentor, my department chair (though I always have to seek her out - she doesn't come find me), and other Language Arts teachers (both in and out of my grade level), but also just other teachers in general. A math teacher, two social studies teachers, a science teacher, an ESL teacher, a special ed teacher, an art teacher, and a PE teacher are members of my go-to group when I want to talk about....well, anything. An individual kid, an entire class, an issue with administration, a conflict between students - whatever it is, I can find someone to talk to. And that has helped tremendously.
Now, I'm at a middle school, and that's one of the biggest differences, I think, that I have more built-in grade-level and departmental structure, but several of these people I've just gotten to know on my own through Friday afternoon drinks or sitting in new groups at faculty meetings.
I think the longer you're at a school, the easier it is to build those support networks, but reaching out to others can only be helpful. It takes time and effort, but it's worth it if it makes your job more enjoyable and thus easier.
(Image credit to hotrodhomepage - though I never share milkshakes with my colleagues. Maybe we should start!)