From "The Conquest of Happiness" 1930, Bertrand Russell ( about love )

One of the chief causes of lack of zest is the feeling that one is unloved, whereas conversely the feeling of being loved promotes zest more than anything else does. A man may have the feeling of being unloved for a variety of reasons. He may consider himself such a dreadful person that no one could possibly love him; he may in childhood have had to accustom himself to receiving less love than fell to the share of other children; or he may in fact be a person whom nobody loves. But in this latter event the cause probably lies in a lack of self-confidence due to early misfortune. The man who feels himself unloved may take various attitudes as a result. He may make desperate efforts to win affection, probably by means of exceptional acts of kindness. In this, however, he is very likely to be unsuccessful, since the motive of the kindnesses is easily perceived by their beneficiaries, and human nature is so constructed that it gives affection most readily to those who seem least to demand it. The man, therefore, who endeavours to purchase affection by benevolent actions becomes disillusioned by experience of human ingratitude. It never occurs to him that the aftection which he is trying to buy is of far more value than the material benefits which he offers as its price, and yet the feeling that this is so is at the basis of his actions. Another man, observing that he is unloved, may seek revenge upon the world, either by stirring up wars and revolutions, or by a pen dipped in gall, like Dean Swift. This is an heroic reaction to misfortune, requiring a force of character sufficient to enable a man to pit himself against the rest of the world. Few men are able to reach such heights; the great majority, both of men and women, if they feel themselves unloved, sink into a timid despair relieved only by occasional gleams of envy and malice. As a rule, the lives of such people become extremely self-centred, and the absence of affection gives them a sense of insecurity from which they instinctivelyseek to escape by allowing habit to dominate their lives utterly and completely. For those who make themselves the slaves of unvarying routine are generally actuated by fear of a cold outer world, and by the feeling that they will not bump into it if they walk along the same paths that they have walked along on previous days.