Happy Valentines day! If truth be told I'm not really convinced about this particular annual ritual. It seems to me that if you have to wait a whole year to give or receive love and affection from your partner then you're doing it wrong. Still, I suppose it makes some kind of focal point for important relationships (or not!) and there are strong evolutionary underpinnings to displays of affection; it's generally good for gene transport down the generations!
These days most people don't realise that the origin of this particular feast day is much darker and sillier than red roses and chocolates. It stems from that eternal religious obsession with martyrdom and death by some form of execution (the bloodier the better) Apparently back in Roman times some geezer called "Valentine" was imprisoned for practising Christianity and later executed, however whilst banged up he supposedly healed the daughter of his jailer (oh really) and wrote her a letter signed "your valentine" (not entirely unreasonable for someone actually called "Valentine").
Of course saintly origins are by definition mythical, they have to involve some kind of suspension of the natural order otherwise no one would take any notice. From Mother Theresa to Valentine of Rome the pattern is a familiar one, take some poor sucker who had a hard life or did something exceptional, add a layer of supernatural (unfalsifiable) hocus-pocus and bingo you've got an excuse for a piss-up and a reason for followers to donate cash to your particular cult. Simple really; one of the first truly viral business models.