Now, my dear little girl, you have come to an age when the inward life develops and when some people (and on the whole those who have most of a destiny) find that all is not a bed of roses. Among other things there will be waves of terrible sadness, which last sometimes for days; irritation, insensibility, etc., etc., which taken together form a melancholy. Now, painful as it is, this is sent to us for an enlightenment. It always passes off, and we learn about life from it, and we ought to learn a great many good things if we react on it right. (For instance, you learn how good a thing your home is, and your country, and your brothers, and you may learn to be more considerate of other people, who, you now learn, may have their inner weaknesses and sufferings, too.) Many persons take a kind of sickly delight in hugging it; and some sentimental ones may even be proud of it, as showing a fine sorrowful kind of sensibility. Such persons make a regular habit of the luxury of woe. That is the worst possible reaction on it. It is usually a sort of disease, when we get it strong, arising from the organism having generated some poison in the blood; and we mustn't submit to it an hour longer than we can help, but jump at every chance to attend to anything cheerful or comic or take part in anything active that will divert us from our mean, pining inward state of feeling. When it passes off, as I said, we know more than we did before. And we must try to make it last as short as time as possible. The worst of it often is that, while we are in it, we don't want to get out of it. We hate it, and yet we prefer staying in it—that is a part of the disease. If we find ourselves like that, we must make something ourselves to some hard work, make ourselves sweat, etc.; and that is the good way of reacting that makes of us a valuable character. The disease makes you think of yourself all the time; and the way out of it is to keep as busy as we can thinking of things and of other people—no matter what's the matter with our self.
William James
depression, habits