He (= The highbrow) will allege that all great achievement has been the outcome of some kind of misery, and he will point out that people like the Samoans, who are said to be happy in childhood and even in adolescence, have never contributed anything to civilisation. If we were all happy, he tells us, we should rapidly sink into the condition of pigs, who, in his opinion, enjoy much more happiness than falls to the lot of intelligent people.
Source: "Should children be happy?" [From: Mortals and Others: Bertrand Russell's American Essays, 1931-1935, v.1 (1975)]
More info.: https://russell-j.com/CHILDHAP.HTM