people base their success relative to others
I’m sure most people know this already, but our happiness is in part based on our professional success (among many other factors), and that success is determined relative to the success of others. More interesting is that who we compare ourselves to is significant. If we compare our position/compensation to our work peers (with whom we have limited emotional attachment), we might feel that our lower salary is “unfair.” However, importantly, if we compare ourselves to our good friends from college, then we’re likely to feel saddened if we are under-performing them.
I’m not convinced feeling bad is always bad. Maybe we should feel bad sometimes. Maybe feeling bad will propel us to a more interesting (and possibly higher paying) position? Or feeling bad might cause us to do something truly great, like pursue a simple solution for problems that lead to significant human suffering (and most innovative solutions are simple and relatively cheap – mosquito nets and seat belts, for eg).