Essay-let: Myths, Fairie Tales, and the Prohibitionary Relationship

There's this thing that shows up in faerie tales. Some of my favorite faerie tales, really. Actually, you can trace its thread from myths through faerie tales, through modern renditions of same, subversion, and probably plenty of modern stories I'm not looking at because I don't have time (not right now, anyway). It goes something like this:

Two people meet, and get together. Maybe they fall in love. Maybe it's an arranged marriage, maybe it's a promise from a person of power [that's kindof an arranged marriage, though], maybe something else. Maybe it's not even a sexual thing at all -- though that's out of scope enough that I'm going to consider it a related category, but out of scope for this essay. But they're together.

Except that there's something wrong -- something you just can't let rest (no story can, nor most humans) -- one of the lovers (usually the man) has a secret. And naturally, there's a prohibition somehow related to the secret -- if the prohibition gets broken, the relationship is doomed.
( Click here for more Beauty/East/Psyche/Bluebeard/Macha thoughts )