Teaching is a funny sort of job. Many are told it's a profession but yet, the teacher is required to follow some pretty strict processes one would not expect for a profession.
Teachers have little control over their work environment.
They are usually controlled by others.
Like Pavlov's dogs they respond to bells and buzzers.
They have to get through a pre-written curriculum and teach stuff they often feel is irrelevant or going out of date.
They have to try to put their own feelings about students on the shelf.
They're a sitting duck for students, parents, administration, boards and government.
They have little say over their job and after a few years of teaching the same subject at the same level many tend to go onto autopilot and go through the motions.
Work hours can be long biting into their family/social life.
Getting caught breaking the law in even a small way can mean the end of their job.
Having to face a class, often with too many students, day after day where the students don't want to be there and are resistive to learning put the teacher under stress because nine times out of ten if the student fails to learn they blame their teacher for being crappy at teaching.
Teachers often feel like they're in a brainwashing experience where they are the target, the end of the chain, in the educational system and are the most expendible person in the school.
Constant awareness of how they relate to students so they lower their risk of being accused of inappropriate behaviour to a student which would cost them their jobs.
A poor image of teachers in the general society
Lower than normal wages for the qualifications they've earned.
Lack of student respect
A general sense of too little appreciation for what they're trying to do.
Very few opportunities for career advancement.

It's a very high risk job to have because some of the smallest indiscretions/mistakes can end in them losing their job and having to break into a whole new area of employment. Poor teaching records can dog a person for years and greatly interfere with gaining a job outside teaching by the very nature of them having had to deal with children.