Basic ideas:

Our desire to avoid pain and experience pleasure tends to push us around if we are not paying attention. When we use introspection to learn about the mind we see that we all try to avoid pain and move toward pleasure in everything we do. This is a huge thing to understand fully.

Pain tells us something is wrong, but we tend to overreact and begin to avoid all pain and discomfort. This creates a treadmill of pain and pleasure. Where we are constantly trying to manage our states of mind by moving away from pain and toward pleasure.