Whether you celebrate this day officially or not.... whether you have a significant other or not....
Today is supposedly dedicated to love, not greeting cards. And most of the love in your life isn't romantic.... I mean, you (hopefully) only have romantic love for one person. But what about your kids, your best friend, your mom?
So pick any person in your life -- your lover, your little brother, your boss, the girl who works at the lunch counter-- and just tell that person you appreciate them. That's it.
Appreciation goes a hell of a lot further than a box of chocolates.