Clearly there is some value to pursuing activities that one finds interesting and even more specifically to trying to find some work or occupation that doesn't make you want to jump off a building. However, the idea of following your dream 1) should be reserved for serious cases, 2) can have deleterious effects on mental health.
1) Just because you happen to either enjoy your job or be relatively content in your everyday life does not entitle you to say that you are following your dream. People following dreams are either people involved in occupations with high barriers to entry and a large ratio of contenders to success where a rational evaluation of one's chances would lead one NOT to try for that success, or they are people who have wanted to be a geologist since they were 5 and now are a geologist having not ever seriously pursued any alternative career path. People following dreams either value the unlikely payoff extremely highly (actors etc.) or value the payoff from performing the activity regardless of the external rewards. Narrowing the definition would exclude most people from qualifying as "following their dream".
2) Surely it is no one's dream to be a middle manager in a regional paper distributor. But that does not mean that you cannot enjoy that job, nor does it mean that you cannot have a successful life if you either do not have a dream or try for a career that you end up not being successful in. The narrative that only people who follow their dreams are happy might mean that people are too rigid in choosing career paths, or that they feel like they have let themselves down if they cannot, for reasons entirely outside their control, pursue their first-choice career. It also has a tendency to overweigh life satisfaction derived from one's job and excluding the possibility of earning money to eat doing one activity (work) and spending one's leisure time doing something fun.
So, my point is that if I end up not getting a tenure-track academic job, everything will be alright (tremble).