What is the source and context of this St. Bernard of Clairvaux quote? The quote


  What we love we shall grow to resemble.


seems remarkably popular. Although it is attributed to St. Bernard of Clairvaux, it doesn't look like anyone who uses it knows which one of his works it came from or what the exact context of it is. 

Can someone who is familiar with his work specify where it comes from?
I have searched the writings of Bernard of Clairvaux, and was unable to find that exact quote. It's possible that your quote was a paraphrase of the original. 

I do know that the closing sentence of "On the Love of God" is "Those who love God are one Spirit with Him." This seems to be close to the meaning, if not the actual words. 

Often in history we don't know everything with absolute certainty, and the best we have is an incomplete picture based on what we know.