It is bad when a married pair bore each other, but far worse when only one of them bores the other.

[Es ist schlimm, wenn zwei Eheleute einander langweilen, viel schlimmer jedoch ist es, wenn nur Einer von ihnen den Andern langweilt.]

Marie von Ebner-Eschenbach (1830-1916) Austrian writer

Aphorisms [Aphorismen], No. 283 (1880) [tr. Wister (1883)]
    (Source)

(Source (German)). Alternate translation:

It's bad enough when married people bore one another; but it's far worse when only one of them bores the other.
[tr. Scrase/Mieder (1994)]