In my opinion although stress will always be part of teaching, there are ways to help prepare teachers avoid or deal with stress in a healthy matter. I think the biggest thing that future teachers need to have before they start their career is more observation and experience in the classrooms. We cannot learn to teach simply by reading a book on teaching. We need to experience it. Student teaching is essential for getting a job, and in my opinion we need more of it. Have students observe in classrooms whenever they can. Have them go to a variety of different schools and simply observe the diverse teachers and students. No two students are alike. However seeing a diverse amount of students with different needs and attitudes may help you to deal with one's own students. You can read all about managing a classroom, but that does not mean that when it comes to applying it you will be able to. I think that is why teachers get so stressed. They are not prepared to deal with the students diverse needs and do not know how to apply what they have learned in the classroom.
I am not saying observation and student teaching is the only thing that will help avoid stress. In general teachers need to be better prepared. They should learn as much as they can about teaching, and from a variety of different angles. What I mean by that is that they should learn several different approaches to one lesson, so that if something does not work out they do not freak out and panic, they simply try something else. I think we also need to be taught how to be flexible, and when something is not working we need to take steps to fix it. I do not have the answers on how exactly we can teach this, but I do have a couple of ideas. For example we could try role playing exercises where we have a student pretend to not know something and have the teacher practice trying to get them to understand. Or think of some steps as a college class to do when your stressed. Such as take a breath, try repeating lesson to see if repetition helps, or change the lesson.
In general I believe teachers are better prepared and have more experience before they are teaching their own class they will be less stressed and better know how to handle it.