The nature of the memory is to hold an impression, agreeable or disagreeable, and therefore a person holds a thought in the mind, whether it is beneficial to him or not, without knowing the result which will come from it. This 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 not knowing that it makes them suffer, nor understanding the reason of their suffering. They go on suffering and yet hold on in memory the very source of their suffering. Memory must be one's obedient servant; when it is a master then life becomes difficult. A person who cannot throw away from his memory what he does not desire to keep in mind, is like a person who has a safe but the key to that safe he has lost. He can put in money but he cannot take it out. All faculties in man become invaluable when a person is able to use them at will, but when the faculties use the person, then he is no longer the master of himself.