Too much of a good thing
Then love me, Rosalind.
Yes, faith, will I, Fridays and Saturdays and all.
And wilt thou have me?
Ay, and twenty such.
What sayest thou?
Are you not good?
I hope so.
Rosalind:As You Like It Act 4, scene 1, 115–124
Why then, can one desire too much of a good thing?
Of all the supposed bawdy puns in Shakespeare's work, this one's authentic. "Thing" was a common enough euphemism for either male or female genitalia, and the context here is certainly suggestive. Having used "too much of a good thing" in all innocence, you might find its original connotation embarrassing.
The indecency of this exchange may also surprise you once you know that Rosalind and Orlando are the quintessential comic-romantic lovebirds, whose goodness and purity are never challenged. The reason Rosalind can speak this way is very complicated, but, briefly put, she's dessed up as a young man and, when she encounters her lover Orlando in the Forest of Arden, she decides to withhold her true identify from him. Yes, you say, but Orlando calls her "Rosalind" here. True, but that's because Rosalind, in the guise of the young man Ganymede, is "pretending" to be Rosalind so that she can train Orlando in courtship and teach him what women are "really" like. Through such play-acting, Rosalind may probe Orlando's intentions, and at the same time put his idealistic notions of courtly lovemaking to the test. She takes on the role of the comic dramatist, scripting a fantasy version of courtship in order to explore and expose its workings.