1. Take a shower.
2. Put some nice clothe on
3. Put some nice cologne on
4. Go to your local mall or hotspot where people hang out.
5. Say "hi" to a couple girls, try having a conversation
6. Get yourself some food
7. Go to the club (awesome on valentine's day)
Valentine's day is when tons of single girls are walking around in packs in malls and other hangout spots (that's how you know they're single, when they're out walking with other girls or by themselves on valentine's day). It's a great day to talk to girls.
Trust me just talking to 1 or 2 will make you feel awesome and you won't remember your oneitis.
That is what I do when i'm feeling down. I dress my best, go out, pick a good restaurant I never been before, eat some good food to reward myself and just get a good vibe going and feel good about myself. Then I approach some girls.