The earliest close match located by Quote Investigator appeared in a work by the German poet Ludwig Jacobowski titled “Leuchtende Tage” published in the August 1899 issue of a literary journal. The title could be rendered as “Bright Days” or “Radiant Days”. One verse rhapsodized about the bright days of the past, and the next verse began with these two lines:

Nicht weinen, weil sie vorüber!
Lächeln, weil sie gewesen!