"Fundamental happiness depends more than anything else upon what may be called a friendly interest in persons and things. ... The kind [of interest in persons] that makes for happiness is the kind that likes to observe people and finds pleasure in their individual traits, that wishes to afford scope for the interests and pleasures of those with whom it is brought into contact without desiring to acquire power over them or to secure their enthusiastic admiration.
The person whose attitude towards others is genuinely of this kind will be a source of happiness and a recipient of reciprocal kindness. ... To like many people spontaneously and without effort is perhaps the greatest of all sources of personal happiness."
The Conquest of Happiness, Bertrand Russell