Shakespeare's Sonnet 93

So shall I live, supposing thou art true,Like a deceived husband; so love’s faceMay still seem love to me, though alter’d new;Thy looks with me, thy heart in other place:For there can live no hatred in thine eye,Therefore in that I cannot know thy change.In many’s looks, the false heart’s historyIs writ in moods, and frowns, and wrinkles strange.But heaven in thy creation did decreeThat in thy face sweet love should ever dwell;Whate’er thy thoughts, or thy heart’s workings be,Thy looks should nothing thence, but sweetness tell.How like Eve’s apple doth thy beauty grow,If thy sweet virtue answer not thy show!

So I will live assuming you are faithful, like a deceived husband. The face of love may still look loving to me, though the love behind it has changed: your looks stay with me, your heart is somewhere else. No hatred can appear in your eyes, so I cannot discover your change there.
In many people's faces, the story of a false heart is written in changing expressions, frowns, and unfamiliar creases. But when heaven created you, it decreed that sweet love should always live in your face. Whatever your thoughts, or whatever happens in your heart, your looks should reveal nothing but sweetness.
How much your beauty becomes like Eve's apple if the goodness inside you does not match your lovely appearance!