Real love is always heroic, because it doesn't count the cost. Its only focus is the good of the one whom we love.
On the other hand, our fallen world is very good at calculating the cost/benefit ratio of every transaction. And the better you get at it, the more the world rewards you with what it has to give: all the stuff that doesn't matter in the end.
Worldly love does the same: everything's fine as long as the other person produces the benefits we think we signed up for. But once those benefits start to decline, the calculations begin, and our hearts harden. We'd be happier with someone else, we think. It's easy to leave and start over. No one will criticize us. Why should we lose our chance of "happiness?" This kind of love is hardly more than the pleasure of an amiable acquaintance, and just as fragile.
In contrast, we can always tell when we're really loved just for ourselves, in the heroic way, when we find ourselves astonished by a lavish gift that we didn't deserve — or perhaps we even deserved the opposite. I'd say the gift of another person's entire life and love, in honor and faithfulness, is one of those gifts.
In 1867, Matthew Arnold wrote "Dover Beach", a haunting poem evoking the "melancholy, long, withdrawing roar" of the Sea of Faith. As a boomer who finished Catholic elementary school in 1964 and then watched my Church falter, I've found the roar all too audible. So here I wait, listening for the whispers of that Sea's invincible return.