"Now, there is no obvious connection between a person's happiness and the way he tells stories about himself. But I think there's a not-so-obvious one. When you insist [...] that you're both lucky and indebted to other people, well, you're sort of prepared to see life as a happy accident, aren't you?
It's just very different than if you tell yourself that you simply deserve all the good stuff that happens to you. Because you happened to be born a genius or suffered so much or worked so hard-- that way of telling the story-- well, it's what you hear from every miserable bond trader at Goldman Sachs, or for that matter, every other a-hole who ever walked the earth."Obviously, one can connect the second half of the quote to a certain "intolerable ass" in Mrs. Dalloway--Hugh Whitbread--who all characters see as an annoyance because he acts superior to everyone.
But I think that the first half of the quote is an accurate description of why Richard Dalloway is the happiest character of the entire novel. Richard is content, and he considers himself lucky to be living like he is. Richard has everything he ever wanted, and in one particular point in the book is he in awe of the fact that his life turned out so well and that he was able to marry Clarissa.
"Indeed, his own life was a miracle; let him make no mistake about it; here he was, in the prime of life, walking to his house in Westminster to tell Clarissa that he loved her. Happiness is this, he thought." (114)
Richard is also happy because he loves and is very proud of his daughter Elizabeth. "But he had his Elizabeth; he adored his Elizabeth." (111)
Richard's happiness and contentment spills over into his relationships with the people around him. Richard--unlike Clarissa, Sally, and Peter--is never described as self-centered or egotistical. Instead, his interactions with others are almost always genuinely friendly (with the exception of Hugh). For example, when Peter is brought up at Lady Bruton's lunch Richard immediately thinks about how much he likes Peter instead of hating him for being in love with Clarissa (104).
In contrast to Richard, I don't think that the other characters of Peter, Clarissa, and Ms. Kilman are truly happy or content. They may have their small moments of happiness, but in the end they're all just judging each other and comparing themselves to the people around them. Peter judges Clarissa for being shallow, Clarissa is mad at Peter for being so critical, and Ms. Kilman hates Clarissa for flaunting her wealth.
None of them are content either. Clarissa is obsessed with hosting parties to distract her from her depression and thinking about what her life would have been like had she chosen Peter, Peter is still not over Clarissa, and Ms. Kilman hates herself because she sees herself as poor and unattractive. They all think that they deserve more than they have, or that they aren't living life they way they wish they could--they're left feeling sorry for themselves and wondering if it's all really worth it. It's no wonder that they're unhappy.