But those who do not practice concentration automatically retain things of great interest, things that impressed their mind most. It is for this reason that some carry with them a fear which has perhaps been there from childhood. It is carried with them through life. Some have a sad impression of disappointment; they carry it throughout life, they retain it in their mind. The mind keeps an impression alive by revivifying it, an impression of revenge, of gratefulness, of success, of failure, of love, of admiration. It is kept there, and the mind-cells give it food to keep it alive. Sometimes this is helpful and sometimes it works against one.