There are two common ways of looking at the world. Many people think of themselves as independent, stand-alone people who can change the world as they like. Another view is that the world around us controls how we think and feel: for example, believing that how our parents raised us has everything to do with how we live later.
The BA view takes ideas from both of these sets of beliefs:
In order to change your mood, you can't only look at the world around you or what's inside you, but at the way that you change and are changed by the world in which you live.