Advice To A Girl by Sara Teasdale.

No one worth possessing
Can

be quite possessed;
Lay that on your heart,
My young angry dear;
This truth, this hard and precious stone,
Lay it on your hot cheek,
Let it hide your tear.
Hold it like a crystal
When you are alone
And gaze in the depths of the icy stone.
Long, look long and you will be blessed:
No one worth possessing
Can be quite possessed.