My sympathy goes out to all who have bad connections with this holiday. It's just so sad to me that anybody should not feel loved. Everyone deserves it, after all.
Nothing is worse than a holiday you aren't allowed to celebrate, lol. And that's pretty much what Valentine's Day is, if you're not in a relationship, you can't come to the party. And like people have already said here, in High School you watched couples "happy in love," knowing it probably wouldn't last past the 12th grade.
But at the same time, there are couples who are genuinely happy and they deserve a day to celebrate that. To try to make them feel bad for that is just petty.
The point is not to worry about them, just concentrate on being happy with your own life whatever your situation and take steps to change it if you feel it's necessary. And again, you never know what is around the corner in life.