The most general survey shows us that the two foes of human happiness are pain and boredom.

[Der allgemeinste Überblick zeigt uns, als die beiden Feinde des menschlichen Glückes, den Schmerz und die Langeweile.]

Arthur Schopenhauer (1788-1860) German philosopher

Parerga and Paralipomena, Vol. 1, “Aphorisms on the Wisdom of Life [Aphorismen zur Lebensweisheit],” ch. 2 “Of What One Is” [Von dem, was einer ist]” (1851) [tr. Saunders (1890)]
    (Source)

(Source (German)). Alternate translation:

The most general survey shows that pain and boredom are the two foes of human happiness.
[tr. Payne (1974)]