I've done some learning about this recently for work and my 3 big takeaways were:

1. People do not want to be useless or hindrances
2. Difficult behaviours often arise from fundamentally good motivations
3. Understanding the motivation behind the behaviour helps you move beyond the difficult behaviour

Also key is, I am (and you are) sometimes the difficult person. Understanding our own core motivation and what unwanted behaviours we tend to manifest are just as important.

This learning was largely based on the book Dealing with Difficult People.