Anybody can google a bit and read that Valentine was a Christian who married people by the christian rite in a time in which Christianism was illegal. His story is called "hagiography" because it's about a saint, and it probably has, in the better case, as much historical value as Beowulf - that is, some things may be true, so if you find coincidences comparing (with no hagiographies) sources, chances are those are true.
He was started being considered defender of the romantic love about two centuries ago but he wasn't. After all, people was already getting married by legal, at the time, rites, according with their own faith, before he started marrying other couples. And the people who came before him was already in love, so he just kind of "marked" them. Worse, the couples he married were formed by roman soldiers and their loved ones. Roman soldiers were banned to marry during service or, more precisely, the government would not consider the union legitimate. A lot of them did marry under the local custom they were in, so probably they didn't care too much about the rite as long as there was a rite. The part I say about Valentine being worse is that, then, he married a lot of couples who didn't believe in his religion, making him hypocrite and incoherent, and probably at least a bit of an indoctrinator.
Anyway, the thing is that today a subset of christians - because the Orthodox church, for instance, does in a different date - celebrate his execution by exchanging gifts and remembering - or pretending to remember - how good is to be together. A lot of non-christians engage in the same customs because it's a nice thing to do and everybody's gonna ask how it went, so why not to fold?
This post is dedicated to those couples who has a nice, working, beautiful relationship:
We hate you
Just kidding. It's beautiful to see couples loving each other so dearly, I just wanted to take some time to say because sometimes it's not easy to understand that from the inside. A loving couple does not need to love each other in a movie sense - think about what Amanda Palmer says in The Art of Asking about she and Neil Gaiman - but you are inspiring just the way you are. If we tell hero stories to remember we can be heroes, guess what that means to your (successful) love stories.
If there are problems, instead of focusing in the problems, please, focus first in why you got and kept together in the first place, for that may be the key to solve those problems or, at the very least, to remember why they're worth solving.
Be as happy as you can today, and please share it with everyone, for we all need some inspiration some time.
Just don't brag people. Make it nice ;)
Have a happy Valentine.