Blessed are the forgetful: for they “get the better” even of their blunders.

[Selig sind die Vergesslichen: denn sie werden auch mit ihren Dummheiten “fertig”.]

Friedrich Nietzsche (1844-1900) German philosopher and poet
Jenseits von Gut und Böse [Beyond Good and Evil], Aphorism 217 (1886) [tr. Zimmern (1906)]
    (Source)

Quoted by Mary Svevo (Kirsten Dunst) in Eternal Sunshine of the Spotless Mind (2004). The character says she found it in Bartlett's.

(Source (German)). Other translations:

Blessed are the forgetful: for they get over their stupidities.
[tr. Kaufmann (1966)]

Blessed are the forgetful: for they shall "have done" with their stupidities too.
[tr. Hollingdale (1973, 1990)]

Blessed are the forgetful, for they are "done" with their stupidities as well.
[tr. Johnston]