The reason why people are very often unhappy in academia is that they don’t live in a way that corresponds to the stage of academic life they are actually in.
Take, for instance, the widely known post-tenure blues. I was having a bad case of them for about a year when I realized that I was trying to keep living as a tenure-track Assistant Professor while being a tenured Associate Prof. As soon as I brought my way of doing things in line with this new stage of my academic life, I became very happy.
Many new tenure-track people suffer because they try to keep living as graduate students when their new status requires something completely different.
Often people are prevented from inhabiting a new stage of their academic life because they are denied tenure or promotion for unfair reasons. Sometimes, people simply don’t know that they are supposed to do things differently after getting tenure or after moving from undergraduate to graduate studies. Every time I was unhappy in my academic life was because I tried to continue doing whatever made me successful in the previous stage and not understanding that a new academic role required a new way of articulating my relationship to the profession and my vision of myself in it.