Sonnet 138, by NY Shakespeare Exchange

When my love swears that she is made of truth,
I do believe her though I know she lies,
That she might think me some untutored youth,
Unlearned in the world's false subtleties.
Thus vainly thinking that she thinks me young,
Although she knows my days are past the best,
Simply I credit her false-speaking tongue:
On both sides thus is simple truth suppressed:
But wherefore says she not she is unjust?
And wherefore say not I that I am old?
O! love's best habit is in seeming trust,
And age in love, loves not to have years told:
     Therefore I lie with her, and she with me,
     And in our faults by lies we flattered be.

Sonnet 138, from The Sonnet Project, by the New York Shakespeare Exchange.

In Western culture, we pay such lip service to truth, and honesty, and openness, coming thus across as naive in the reality of life.  A couple in love may choose to dispense with the truth of age - frank wrinkles, lackluster hair - in order to forge their romance.  Interestingly, while there is a striking difference in age between the two, even the younger of the two is evidently conscious, albeit privately, of her age.  Finally, a tour de force of a pun around "lie" is perfect for the sexual denouement in the couplet.