In plain English

When thou shalt be disposed to set me light 
And place my merit in the eye of scorn,
Upon thy side against myself I'll fight
And prove thee virtuous, though thou
art foresworn.
With mine own weakness being best acquainted,
Upon thy part I can set down a story
Of faults concealed wherein I am attainted
That thou in losing me shall win much glory.
And I by this will be a gainer too,
For, bending all my loving thoughts

on thee,

The injuries that to myself I do,
Doing thee vantage, double-vantage me.

In many's looks, the false heart's history

Is writ in moods and frowns and wrinkles strange,

But heaven in thy creation did decree

That 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.

William Shakespeare

Sonnets 88, 93