Ah, happiness, that elusive state. Philosophers, theologians, psychologists, even economists, have long sought to define it, and since the 1990s, a whole branch of psychology—positive psychology—has been dedicated to pinning it down and propagating it.
Questions of personality have vexed mankind from the dawn of personhood: can people change? How do others perceive me? What is the difference between normal and pathological behavior? One's personality is so pervasive and all-important that it presents a clinical paradox of sorts: it is hard to assess our own personality, and impossible to overlook that of others.