Every good restaurant and bar is going to be booked up solid with couples on Valentine's Day night through the weekend. You can still treat yourself, but do it when the vibe is lighter. Eat a hearty breakfast or a delicious lunch.
Pop into an animal shelter. Seriously, they need valentines and they will love you so much for being there.
Guess what's empty on Valentine's Day... The Gym!!!! Get in there, get a great pump, don't be bothered needing to wait for the squat rack or a bench.
If you're not an animal person (see #2), then be a people person! Volunteer at your local homeless shelter, soup kitchen, shovel the snow for old people, do whatever. You might be single, but you're not forgotten.
This is honestly the most important... do things to take your mind off of "Single's Awareness Day". Fill your time and you'll get through it fine. You got this... we know you do.