ELMIRE: No, amorous men are gullible. Their conceit
So blinds them that they’re never hard to cheat.

[Non; on est aisément dupé par ce qu’on aime.
Et l’amour-propre engage à se tromper soi-même.]

Molière (1622-1673) French playwright, actor [stage name for Jean-Baptiste Poquelin]
Tartuffe, or the Hypocrite [Le Tartuffe, ou L’Imposteur], Act 4, sc. 3 (1669) [tr. Wilbur (1963)]
    (Source)

When her maid is concerned that Tartuffe will see through Elmire's stratagem.

(Source (French)). Alternate translations:

No, People are easily Dup'd by what they love, and Self-love helps 'em to deceive themselves.
[tr. Clitandre (1672)]

No; people are easily duped by those whom they love, and conceit is apt to deceive itself.
[tr. Van Laun (1876)]

No, we are easily duped by those we love, and we deceive ourselves through our own conceit.
[tr. Wall (1879)]

No, people are easily duped by what they like; and self-love helps them to deceive themselves.
[tr. Mathew (1890), 4.2]

No; people are easily duped by those whom they love. Self-love leads the way to self-deceit.
[tr. Waller (1903)]

Oh no! A lover's never hard to cheat,
And self-conceit leads straight to self-deceit.
[tr. Page (1909)]

No, one is easily fooled by one's belovèd,
And self-conceit will end in self-deception.
[tr. Bishop (1957)]

Oh, no! A lover is not hard to cheat,
And self-deception springs from self-conceit.
[tr. Frame (1967)]

He loves me, and he's also vain,
That double drug will dull his brain.
[tr. Bolt (2002)]

No, it's easy to be fooled by what we want; our vanity is always ready to betray us.
[tr. Steiner (2008)]

We long to be fooled by the one we love,
And pride lends a hand in its own downfall.
[tr. Campbell (2013)]