Ada Cambridge - Vows

Nay, ask me not. I would not dare pretend
To constant passion and a life-long trust.
They will desert thee, if indeed they must.
How can we guess what Destiny will send -
Smiles of fair fortune, or black storms to rend
What even now is shaken by a gust?
The fire will burn, or it will die in dust.
We cannot tell until the final end.

And never vow was forged that could confine
Aught but the body of the thing whereon
Its pledge was stamped. The inner soul divine,
That thinks of going, is already gone.
When faith and love need bolts upon the door,
Faith is not faith, and love abides no more.

Ada Cambridge

http://www.poemhunter.com/poem/vows-11/