There are two types of people in the world. Although they have【D1】______ of

There are two types of people in the world. Although they have(21)equal degrees of health and wealth and other comforts of life, one becomes happy, and the other becomes(22)miserable. This arises from the different ways in which they consider things, persons, and events, and the resulting effects upon their minds.
    People who are to be happy fix their attention on the(23)conveniences of things, the pleasant part of convention, the fine weather. They enjoy all the cheerful things. Those who are to be unhappy think and speak only of the(24)contrary things. Therefore, they are continually(25)discontented. By their remarks, they sour the(26)pleasure of society, offend many people, and make themselves disagreeable everywhere. If this turn of mind were found in nature, such unhappy persons would be the more to be pitied. The(27)tendency to criticize and to be disgusted is perhaps taken up originally(28)by imitation. It grows into a habit, unknown to its possessors. The habit may be strong, but it may be cured when those who have it are convinced of its bad effects(29)on their interests and tastes. I hope this little warning may be of service to them, and help them change this habit. Although in fact it is chiefly(30)an act of the imagination, it has serious consequences in life since it brings on deep sorrow and bad luck.