You learn a lot about people when they don't get what they want.
With time, we get to see what people can be. Their true colors will show. Some people are good in the beginning, in the present, and the days ahead. And some good temporarily, and when they are done using, then they treat you very bad. Pay attention to how someone behaves and treats you. If they don't treat you well or respect you, let that person go.
I think in ourselves as well. I am constantly learning more and more about my nature and tendencies in different life circumstances.