This is a part of teaching by Ilchi Lee on Focus and Attachment.

Let’s say that my brain remembers some intense pleasure. Then it will want to reproduce that pleasure. Or, if it remembers some intense pain, it will want to avoid that pain. For example, if a person has satisfied her need for recognition and control, and so has the pleasurable memory of feeling better as a result, her brain will try to satisfy those needs again, to receive recognition or control others. If someone had a very intensely painful experience with a hard training, his brain will want to flee in fear on just hearing the word “hard training”. Human beings have bodies, and so they have pleasures that come out of their desires. They have desires for food, sex, sleep, leisure, and they have an ego; they also have the pleasure of feeling better when they satisfy these things. Physiologically, the brain seeks to reporduce those pleasures according to the information that is stored in it.

As a result, it concentrates on various desires in ways that are different from what I intend. That concentration doesn’t drop off easily, either. They lay hold of my mind and won’t let go. This is attachment. And they seek to avoid pain in circumstances where pain is anticipated. That’s why resistance arises in my brain when I want to concentrate on my wish to do a hard training. This is the brain’s emergency brake. All of these pheonomena arise based on the memories and animal desires of the brain. At such times, I am unable to concentrate as much as I would like to concentrate. To put it another way, the brain is focused by emotion and desire. My mind is led about by them.