According to twelfth century writer, Andreas Capellanus, there are specific rules to love. He lists them off in his book The Art of Courtly Love, first written at request of the Countess Marie of Troyes, daughter of Eleanor of Aquitaine.
Here are just a few:
Marriage is no excuse for not loving.
No one can be bound by a double love.
No one should be deprived of love without the very best of reasons.
Love is a stranger in the home of avarice.
Good character alone makes a man worthy of love.
Hmmm…. Not bad Andreas.