The nature of the memory is to hold an impression, agreeable or disagreeable, and therefore a person holds a thought in mind, whether it is beneficial to him or not, without knowing the result which will come from it. It is like a child who holds a rattle in his hand and hits his head with the rattle and cries with the pain, and yet does not throw the rattle away. There are many who keep in their mind a thought of illness or a thought of unkindness done to them by someone and suffer from it, yet now knowing what it is that makes them suffer so, nor understanding the reason of their suffering.