My glass shall not persuade me I am old, So long as youth and thou are of one date, But when in thee time's furrows I behold, Then look I death my days should expiate: For all that beauty that doth cover thee Is but the seemly raunment of my heart, Which in thy breast doth live, as thine in me. How can I then be elder than thou art? O therefore, love, be of thyself so wary As I not for myself but for thee will, Bearing thy heart, which I will keep so chary As tender nurse her babe from faring ill: Presume not on thy heart when mine is slain; Thou gav'st me thine, not to give back again.