1. Do what you love. Just make sure that "what you love" happens to be health insurance and a paycheck that covers basic expenses like rent, Diet Sprite, and weed that doesn't suck.
2. Don't try to self-diagnose your own diseases on the internet. Your mind will formulate Google searches to fit a pattern connected to your "symptoms," and suddenly you'll be convinced that you have so little time left to live that you shouldn’t even bother buying a bunch of unripe bananas. Unless you don't have health insurance (see #1 above). Then Dr. Google is your BFF.
3. Read lots of blog posts, especially if they're in the form of lists and open letters. And especially if they're written by other women (if you’re a woman); parent (if you’re a parent); divorced (if you’re divorced); married (if you’re married) or single, (if you’re single). In short: try to find something—anything—written online--by anyone (doesn't matter who) that either validates your experience or makes you feel glad you're not as fucked up as the person who wrote that thing.
4. Go on Facebook and unfriend everyone who has a better body than you and/or looks better than you and happier than you in pictures, especially professional engagement and/or wedding photos that are taken mid-laughter-with-shiny-white-teeth or mid-jump-in-the-air-while-barefoot-in-the-sand. Also unfriend anyone who is actively trumpeting a happy experience (e.g. pregnancy, promotion, trip to Italy), that you are not currently experiencing, but that you covet with a blind and bitter envy bordering on rage. Because let's face it, you can't quit Facebook--but you can control it. Sort of.
5. Break something on purpose every now and then. Like something valuable such as a laptop or an iPhone, or perhaps a Faberge egg. Something that can't easily be put back together or replaced because it's unique, expensive, or the pieces are too small. The first draft manuscript of your novel is a good one. Tear it up, pour gasoline on it, and burn that mother to the ground. See? Didn't that feel good? What a rush!
6. Unsubscribe from your college alumni and/or graduate school alumni magazine.
7. Attend your high school, college, or graduate school reunion (5, 10, 15, 20) and count the number of people who appear more miserable than you and/or are aging badly. Make several snap-judgments and superficial calculations about their lives in order to make yourself feel better about your own. (This one's a gamble, though, as you could just as easily encounter someone who makes you feel like more of a failure, rather than less of one).
8. Travel to exotic places and document your travels extensively on Instagram. Unfollow anyone else on Instagram who travels to exotic places and documents their travels extensively on Instagram. That way you won't inadvertently make an invidious comparison that acts as an obstacle to your happiness.
9. Spend at least some time each day waiting for the other shoe to drop and entertaining between one and three catastrophic fantasies. That way, when one of these fantasies becomes reality (as it inevitably will), you might feel slightly more prepared for it.
10. Make a little time for yourself each day. Whether it's immersing yourself in a good book, going to a yoga class, heading outside for a run, throwing a ceramic bowl, meditating, or just crying dolefully into your pillow after masturbating and listening to The Velvet Underground while thinking about everything that could have been and mindlessly consuming a pint of Ben & Jerry's Phish Food ice cream, it's always important to take those extra special little moments for yourself in life.