Many people prolong an illness by giving way to pessimistic thoughts. One will often find that for those who have suffered for many years from a certain illness, that illness becomes so real that its absence seems unnatural. They believe illness to be their nature, and its absence is something they do not know; and in that way they keep the illness in themselves. Then there are pessimistic people who think that misery is their lot in life, that they were born to be wretched, that they cannot be anything else but unhappy, that heaven and earth are against them; but they themselves are their misery, and pessimism belongs to them. Man's life depends upon the object of his concentration, so if he concentrates upon his misery, he must be miserable. A person who has a certain habit of which he does not approve, often thinks he is helpless before it as it is his nature; but nothing is man's nature except what he makes for himself.