Forbes has offered a list of 13 strategies used by “mentally strong” people. Seems like an excellent list:

1. Waste Time Feeling Sorry for Themselves.
2. Give Away Their Power.
3. Shy Away from Change.
4. Waste Energy on Things They Can’t Control.
5. Worry About Pleasing Others. Know any people pleasers?
6. Fear Taking Calculated Risks.
7. Dwell on the Past.
8. Make the Same Mistakes Over and Over.
9. Resent Other People’s Success.
10. Give Up After Failure.
11. Fear Alone Time.
12. Feel the World Owes Them Anything.
13. Expect Immediate Results.

Bonus: Alternet has offered the 14 habits of miserable people:

So if you aspire to make yourself miserable, what are the best, most proven techniques for doing it? Let’s exclude some obvious ways, like doing drugs, committing crimes, gambling, and beating up your spouse or neighbor. Subtler strategies, ones that won’t lead anyone to suspect that you’re acting deliberately, can be highly effective. But you need to pretend that you want to be happy, like everybody else, or people won’t take your misery seriously. The real art is to behave in ways that’ll bring on misery while allowing you to claim that you’re an innocent victim, ideally of the very people from whom you’re forcibly extracting compassion and pity.

Here, I cover most areas of life, such as family, work, friends, and romantic partners. These areas will overlap nicely, since you can’t ruin your life without ruining your marriage and maybe your relationships with your children and friends. It’s inevitable that as you make yourself miserable, you’ll be making those around you miserable also, at least until they leave you—which will give you another reason to feel miserable. So it’s important to keep in mind the benefits you’re accruing in your misery.

Honing Your Misery Skills

Let’s get right to it and take a look at some effective strategies to become miserable. This list is by no means exhaustive, but engaging in four or five of these practices will help refine your talent.

1. Be afraid, be very afraid, of economic loss.
2. Practice sustained boredom.
3. Give yourself a negative identity.
4. Pick fights.
5. Attribute bad intentions.
6. Whatever you do, do it only for personal gain.
7. Avoid gratitude.
8. Always be alert and in a state of anxiety.
9. Blame your parents.
10. Don’t enjoy life’s pleasures.
11. Ruminate.
12. Glorify or vilify the past.
13. Find a romantic partner to reform.
14. Be critical.