You could say that the pursuit of happiness, rather than of salvation or immortality, is the religion of the modern world, and therapists its priests. The paradox we confront, therefore, is that happiness is a key concept in fiction, as in life, but seldom represented directly or extensively. It is always present in the text as something desired, lost, aspired to, hoped for, remembered, coveted, mourned - but rarely as something continuously experienced. The reason is very simple. There is no conflict in happiness.
Happiness is the opposite of conflict.
It is enjoying life without wishing that it were different, without regretting the past or worrying about the future. There is another reason why the literary novel has not dealt very extensively with happiness, and that is the belief, especially characteristic of the modern literary imagination, that any truthful depiction of life will reveal that the pursuit of happiness is in vain. The horrific events of modern history have reinforced this view. A great deal of modern literature has been concerned with the darkest, bleakest, most sordid aspects of human experience, and has implied that anyone who claims to be happy, whether they have religious faith or not, must be in denial, or a state of bovine insensitivity. There is a view, which Greene shared, that artistic creativity is a kind of compensation for an exceptional capacity for unhappiness.