There's nothing wrong with being alone on Valentine's Day and don't think that everyone has romantic plans that time. They don't, it just seems that way to you.
You know, some have them and do it out of sheer habit, not love, others just because it's the day they can tell others they were part of the euphoria of Valentine's Day. And in this case it is better not to.
This year you can fall in love with yourself, you go for lunch or shopping and treat yourself to something you don't do every day. Treat yourself to a little more!
Don't watch romantic movies if you're sad
If you're determined to stay home, watch a movie that really interests you, is unusual, or educational, or has a strong character at the center of the story, or some kind of comedy.
Go out with friends
You are definitely not the only single person in this world. And while your best friend may be married or in a long-term relationship, you know plenty of people who are single. You're single, but you're not lonely. Pamper yourself.
Treat yourself to a bath, a trip, buy a bottle of good wine, and if the opportunity arises, go out and enjoy the company. You don't have to go out with the goal of meeting someone, but to have a good time.
Do something concrete for yourself
Make some long-term investment. Pay for photography lessons, tennis lessons, whatever you want to improve your skills. Simple, do something for yourself, something that makes you feel good.
Don't call your ex!
Never! Because you won't call her because you're in love with her, but because you want to have a relationship with someone again. Do you really want it to be that person? Better call your parents, relatives, friends, pizza delivery and order it, but never call your ex-partner.
You are a wonderful person, and when the time is right, you will meet "her" too.