Psychologically there are two dangers to be guarded against in old age. One of these is undue absorption in the past. It does not do to live in memories, in regrets for the good old days, or in sadness about friends who are dead. One's thoughts must be directed to the future, and to things about which there is something to be done. This is not always easy; one's own past is a gradually increasing weight. It is easy to think to oneself that one's emotions used to be more vivid than they are, and one's mind more keen. If this is true it should be forgotten, and if it is forgotten it will probably not be true. The other thing to be avoided is clinging to youth in the hope of sucking vigour from its vitality. When your children are grown up they want to live their own lives, and if you continue to be as interested in them as you were when they were young, you are likely to become a burden to them, unless they are unusually callous. I do not mean that one should be without interest in them, but one's interest should be contemplative and, if possible, philanthropic, but not unduly emotional. Animals become indifferent to their young as soon as their young can look after themselves, but human beings, owing to the length of infancy, find this difficult.