As I deepen my understanding through the practice of Bramacharya (abstinence) I feel compelled to share two exquisite teachings:
Shanti seva, for example, in his much-beloved Bodhicaryāvatāra (pg. 117), writes:
For what person is it appropriate to be attached to impermanent beings, when that person is impermanent, when a loved one may not be seen again for thousands of lives?
Not seeing them one finds no pleasure and cannot remain in meditative concentration, and even when one does see them one is not satisfied. One is tormented by longing, just as before.
One does not see things as they really are. One loses the sense of spiritual urgency. One is consumed by that grief, by hankering after contact with the one who is loved.
While uselessly preoccupied with that person, life gets shorter by the minute. For a friend who does not last, the everlasting Dharma is lost.
His Holiness the Sixth Dalai Lama, in one of the eloquent poems for which he is best known, applies this logic more directly to romantic love as well:
If I could meditate upon the dharma
As intensely as I muse on my beloved
I would certainly attain enlightenment
Surely, in this one lifetime