Love Not Me For Comely Grace

Love not me for comely grace,
For my pleasing eye or face;
Nor for any outward part,
No, nor for my constant heart:
  For those may fail or turn to ill,
  So thou and I shall sever.
Keep therefore a true woman's eye,
And love me still, but know not why;
  So hast thou the same reason still
  To doat upon me ever.