DO find someone else to hang out with sometime during the day. Being alone just makes you paranoid and bitter. (Ask me how I know!)
DON'T make that someone else to hang out with someone who used to be your significant other or who you wish was your significant other. That's just awkward.
DO eat some frickin' chocolate. Unless dietary restrictions prevent you.
DON'T drink or otherwise chemically alter yourself into a stupor. It makes things worse, and you might do something stupid.
DO do something you enjoy. Especially if it's horribly geeky. For example, I will be watching Doctor Who all day and then reading Harry Potter until I fall asleep. I may throw in a Stephen Fry podcast. Heck yes.
DON'T give into anyone who tries to make you feel bad for not having a significant other. Same for anyone who tries to pity you. Not that I'd know, but significant others sound lame. I have a feeling they'd object to my talking about yarn all the time and making jokes about Daleks.
Armed with these suggestions, I hope you have an excellent Day That Shall Not Be Named. See you on the flipside.