I grant I never saw a goddess go; My mistress, when she walks, treads on the ground. And yet, by heaven, I think my love as rare As any she belied with false compare.
In different terms, Shakespeare is saying that the mistress is not exactly conventionally attractive in any way, but he still believes she is simply and elegant as any other lady. Only the mistress, unlike these other ladies, is not holding her attraction ‘talked up’ by unnecessary and laughable comparisons.
My mistress' eyes are nothing like the sun; Coral is far more red than her lips' red; If snow be white, why then her breasts are dun; If hairs be wires, black wires grow on her head. I have seen roses damasked, red and white, But no such roses see I in her cheeks; And in some perfumes is there moredelightThan in the breath that from my mistress reeks. I love to hear her speak, yet well I knowThat music hath a far more pleasing sound;
In this segment of the sonnet, the author is diminishing his mistress. Comparing her to the beauties of nature, but never in her favor. Comparing her chests to white snow, and stating that her bosoms are dun-colored, relating her cheeks with roses, and accusing her cheeks not to be red enough like a rose, and insulting her more and more.
Coral is far more red than her lips' red;
Again, he is comparing the mistress with nature. This time comparing her lip colors with corals saying that even corals are more red than her lips.
My mistress' eyes are nothing like the sun;
The narrator is saying that his mistress's eyes looks nothing like the sun, trying symbolically say that this mistress, who can be a lover or girlfriend, has ugly eyes.