Competition in department among professors
There is always pressure to succeed in life, and further, people who get prestigious jobs are often those who are self-motivated to do exceedingly well.  I've also noticed athletes who cannot have "fun" playing softball or whatnot because they are so upset when they or their teammates play badly.  Unfortunately, these are the types of people who often win in competitive situations.

There are enormous differences between departments both within and across institutions. Believe me, even one crop of PhD students or a year of undergraduates can make things more or less pressured, let alone university or department executives.

Why do people become academics?  Two reasons: because they love what they do, or because they feel like they can't do anything else.  The latter is nuts. If you do not love what you are doing, get out now.  Anyone who can make it to a PhD let alone to faculty can get a good job in industry. But academia really is about getting to spend at least some of your time pursuing and talking about things that really truly interest you, and might change the world.