Ever since the beginning of time, man has wrestled with identity, and more specifically, the struggle and divide between the mind and the body. Some may argue that the two are separate, that each side of the person is responsible for different feelings, functions, and desires. But the more that scientists look at the mind and body, the more they realize how closely related the two are. The mind-body problem if you will.
Another way to look at it is the divide between the heart and the brain. People often reference following their heart, as a way to define acting upon desires that are not necessarily logical. So what you get is people thinking that following either the heart or the brain precludes the other.
In reality, identity does involve the two parts of humanity, but they are very closely connected, and one does not preclude the other. Even when following your heart, there is some logical benefit for doing so. For example, loving somebody that you know is not right for you. Some might say that you are following your heart to your own detriment, but in reality, the mind plays a role too.
Somewhere, deep in the mind of the person having this thought, there is a logical reason for it. Perhaps they think by sticking with this person, they can find love, something that the mind would greatly appreciate. So by examining our humanity, we have come to learn that there is really no divide between the mind and the body, that they are all part of who we are.