Entirely human and peculiar to the cleverest--the battle between reality and seeming, the attempt to people the arid wastes of the commonplace with philosophic thought--the unhappiness and despair that arise from comparing the unconcern of the majority with one's own painful unrest, from the knowledge that the results of striving do not express the effort made--that human life is but a ceaseless and unworthy rotation, in which the bad are always to the fore, and the good fall behind ... as pessimism, melancholy, world pain (Weltschmerz)--that tormenting feeling which mocks all attempt at definition, and is too vitally connected with erring and striving human nature to be curable--that longing at once for human fellowship and solitude, for active work and a life of contemplation.
Petrarch knew too the pleasure of sadness, what Goethe called 'Wonne der Wehmuth,' the dolendi voluptas.
Lo, what new pleasure human wits devise!
For oftentimes one loves
Whatever new thing moves
The sighs, that will in closest order go;
And I'm of those whom sorrowing behoves;
And that with some success
I labour, you may guess,
When eyes with tears, and heart is brimmed with woe.