According to Julie

Listen to the right music. If you're like me, having the wrong song play in shuffle mode when you're already feeling bad can ruin your evening. Have your own version of a joyous playlist ready. The songs on the list should not remind you of whatever the Problem is, and they should probably not be happy love songs. In fact, you might want to include something really angry in there, just to get those feelings out of your system. It's kind of like when you have a song going through your head, and the only way to get it out is to actually listen to it. Alternatively, listen to something you've never heard before, either without lyrics or with lyrics you can't understand.

Curl your hair. If your hair is straight, use velcro rollers in damp hair with mousse and really strong styling spray (or L'Oreal StudioLine Indestructable Gel with so-called "Style Memorizing Effect For Bounce-Back Style"). Wear the rollers while you follow one of the next tips on the list, and then take them out to look like this:

Actually, this picture was taken the morning after I used velcro rollers. Bounce-back style indeed.

I find it hard not to smile when I look like this. I don't know if straightening your natural curls will have the same effect, but maybe it's just the drastic change. And it's not as cliché as cutting your hair short, like girls who desperately need a change always do in the movies.

Watch Hard Candy. A man brings an under-age girl he met in a chat room, back to his apartment and has a few drinks with her. He then wakes up to find that she's drugged him and now he's tied to a table, naked from the waist down except for a bag of ice, and she's standing over him saying she wants to do some "preventive maintenance". The plot can also be summed up by this photo. Important: if you're a guy, don't watch this. It is Not Safe For Life.

If you're not THAT angry, and you'd rather just laugh, watch Hot Fuzz. It is really, really, really, really funny. As in I laugh hysterically every time I see it. And added bonus: the only couple who are happily in love are decapitated. (I don't condone violence BTW. When someone stamped on my foot on purpose in a club, while wearing stilettoes, I hid in a coat room rather than punch her. And three minutes of No Country for Old Men left me rubbing my throat for about a week to check if I was still breathing and not being strangled by the chain between someone's handcuffs. But this is a good time for a violent revenge fantasy. Just make sure your visual entertainment is violent, NOT your real-life actions.)

Plan a party. Everyone says keep busy, and this is a good way to do so. Plus, it gives you a reason to clean your apartment, wear something that makes you look amazing and surround yourself with friends. Which brings me to the next tip:

Surround yourself with people who know you're amazing. It's an obvious one, but it should be on the list. Make sure you have a few allies in this party-planning process. People who know that you can't handle negative stress or not having enough guests. People who will not ask you where your date is or randomly not show up or leave laughably early to go home with their boyfriends. If you have pets or younger siblings who look up to you, hang out with them more than usual. Little creatures who think you invented being awesome are exactly what you need right now.

Make new friends superficial coffee-drinking buddies. The best part about these new people is that when they ask you how you're doing, they don't want an honest, detailed answer. Find a brand new acquaintance who thinks your life is perfect. Force yourself to keep up that illusion for as long as you can. It's not fake, it's therapy: Smiling and focusing on the positive is good for you. You can always share your deep, dark secrets when you've known them for a few months.

Dress really, really well. At times like this, you should at least make sure you look great. Dress up just a little more than necessary for any occasion. Enjoy the compliments. Notice the stares. (Also, there is always designer lingerie on sale somewhere. This is the right time to buy some. The Problem has no idea what he's missing.) If you feel ugly, follow these tips.

Be rude. If you're angry, be angry. If you're sad, be sad. How upset you are is up to you. It is not up to anyone else, or to any unwritten rules. You can (and should) pretend to be ok some of the time, for your own sake, to distract yourself. But don't officially tell people who are supposed to care that you're ok until you are. Because they will believe you too soon. And never, ever pretend to be ok for the sake of the person or people who hurt you. Forgive them for your own sake, not for theirs.

Go to concerts. And to the movies, and the opera, and the theater and restaurants. Experience! Remind yourself that the world is an interesting place to be.

Flee the country. Ideally, if you're the right age, go to Ufton. You'll be surrounded by cheerful, British theater people who hug you. A lot. And you'll learn new things and make new friends and one day, you'll just realize you're over him. At least, in my experience. But seriously, travel. It could be a long weekend visiting a friend who lives an hour away by train or actually moving to another continent. I don't think I've ever regretted going somewhere else.  

If none of these work, and it's been longer than say, a month, go to your doctor. Life is not supposed to be this hard.

P.S. If a break-up is the issue, there are more specific tips for that here.