A lot of tenured professors feel like this. Generally these are smart, hardworking, organized people. They wasted all their talent and career working inside a stupid system geared towards taking advantage of, and propping up stupid people. As you look back on your career, its full of nothing. Young people just brown nosing, or doing the bare minimum to get through class. A sea of mediocrity. In the social media area, you may find a student that you labeled as an idiot, doing far better in every aspect of his life, more money, hotter wife, all at a younger age. That shit can eat you up if you have an ego on you. Compare this to an entrepreneur, or even a good blue collar worker. You get much more dynamic relationships in those kinds of fields with your coworkers and clients. You can think back about the deals you made, the shit you got everyone out of, the great feeling you get one someone tells you how awesome you are and hands you a big ass check. He never got any of that. Its annoying when a guy like him becomes a teacher, you can set students back, or be the straw that breaks someone. The only job more dangerous for a guy with that personality type to have is cop.