“What the eye doesn't see, the heart doesn't grieve.”

Source: Diary of a Drug Fiend

Source: Lady Chatterley's Lover

Source: All the Names (1997), p. 185

Variant: It will grieve me so to the heart, that I shall cry my eyes out.
Source: Don Quixote de la Mancha (1605–1615), Part I, Book III, Ch. 11.

Source: Why We Broke Up

Misnad al-Imām al-Hādī, p. 304.
Regarding Knowledge & Wisdom, General

Variant: Boys think girls are like books, If the cover doesn't catch their eye they won't bother to read what's inside.

Quem vê, Senhora, claro e manifesto
o lindo ser de vossos olhos belos,
se não perder a vista só em vê-los,
já não paga o que deve a vosso gesto.
Lyric poetry, Não pode tirar-me as esperanças, Quem vê, Senhora, claro e manifesto

Enchantment (1999)