In the excellent collection This Explains Everything, edited by John Brockman, two of the contributors provide an explanation for why this is easier said than done. David M Eagleman, a neuroscientist at Baylor College of Medicine, writes of "overlapping solutions", where the brain is not made up of separate parts that deal with different activities – ie. one area for language, another for face recognition etc. Instead, he says: "The deep and beautiful trick of the brain is more interesting. It provides multiple, overlapping ways of dealing with the world."
This is echoed by the psychology researcher Judith Rich Harris, who explains that this is the root reason for a good deal of the drama in our lives and our literature, movies, plays and soap operas. It is what leads one part of us to do something that another part of us knows is wrong.