All I ever learned about people, I could have learned a lot faster by studying Myers-Briggs - the popular personality test developed by its namesakes which reduces all 6 billion people in the world to a mere 16 personality types.
There is also an interesting book called "Using Myers Briggs in the Workplace", which as a Project Manager I found quite useful in adapting to the varying personalities one can face in their job.
For example, every work place has that one person who is difficult to work with - that type of person who doesn't seem to want to go along with the rest of the team on any initiative. If you find yourself with one of these people, perhaps you have an idealist on your hands. If that's the case then there is no other way of dealing with the situation than directly: Have a conversation with the disruptor and set expectations. Do not dictate or give ultimatums as this does goes against their core beliefs. Work within their idealist belief system, and frame the situation in terms they can understand.
By the way, I took this test and turns out I am known as "The Counsellor" which is accurate.