Like Paul Newman and Joanne Woodward or Jimmy and Rosalynn Carter, some couples are so well-matched, they almost seem fated to be together. Others are so incompatible, you have to scratch your head wondering how they even got together in the first place.
Below, psychologists and other relationship experts share nine types of couples who simply don't have what it takes to go the distance.
1. The power-imbalanced couple.
No one wants to be the less emotionally invested partner. It's a true power imbalance, said Kristin Davin, a New York City-based psychologist, and it really doesn't bode well for your relationship in the long-term.
"If you find that you're always the one doing the [emotional] heavy lifting, it changes your relationship dynamic," Davin told HuffPost. "People become resentful. They experience inequality in the relationship and the heavy lifter feels like the relationship is more work than it should be."
Relationships take effort, care, and intention but at the end of the day, your partnership should add to your life, not feel like part of the daily grind, she said.
2. The checklist couple.
It's smart to have a handful of qualities you're certain you want in a future partner. That said, don't forget about good old-fashioned chemistry and shared values while looking for Mr. or Mrs. Right, said Virginia Gilbert, a marriage and family therapist based in Los Angeles.
"It’s not that there’s anything wrong with marrying a tall, handsome, gluten-free, Ivy League-educated venture capitalist who just so happens to write poetry in his spare time," she said. "But if you don’t share basic values (for instance, you believe in monogamy and -- oops -- he doesn’t), you need to rip up your old checklist and write a new one with qualities that truly matter."
3. The couple that threw their checklist out the window.
On the other hand, the couple who settles for each other and disregards their deal breakers entirely isn't likely to stay married either, said Marcia Naomi Berger, a psychotherapist and the author of Marriage Meetings for Lasting Love.
"These are essentially irreconcilable differences," she told HuffPost. "That's why it's crucial to talk about needs in relationships before tying the knot. For instance, if one partner wants to have children and the other doesn’t -- and neither is willing to let go of their position -- they should not get married."
4. The self-sabotaging couple.
She cheated on him, so he "got even" by sleeping with his co-worker. He refused to go to his boyfriend's family dinner, so now they refuse to go to each other's family gatherings at all, purely out of principle.
In a relationship, playing tit for tat is the ultimate sabotaging act, said Marina Sbrochi, the author of Stop Looking for a Husband: Find the Love of Your Life.
"This game continues, rinse and repeat, until someone finally grows up and gets the courage to leave all the arguments behind them, right there with the dead relationship."
5. The hot-and-heavy-but-not-much-else couple.
"You have to date for a long while before establishing that you're truly compatible," she said.
6. The May-December couple.
For most of us, age is more than just a number when it comes to relationships, Sbrochi said.
"The vast majority of people shouldn’t be dating someone thirty years up or down; the stage of development is just too different," she told HuffPost. "Unless you truly are stuck in your 20s, try to date someone within your life stage. Being young may have been fun but when you become emotionally mature enough, you won’t need to relive that stage of your life vicariously through someone else."
7. The narcissistic couple.
Not everyone you date who's slightly self-absorbed has full-blown narcissistic personality disorder (NPD). But people who truly fit the narcissistic personality type are very difficult to be in a relationship with, Berger said.
"It simply won't work if one partner is too self-absorbed to feel and express empathy for a spouse," she said. "Empathy is an essential ingredient for a lasting, fulfilling marriage. Eventually, the emotionally neglected partner will want to end the marriage."
8. The couple who refuses to talk about money.
Don't assume any money issues you have individually or as couple will get resolved once you're married, said Berger. Financial conversations may not be the sexiest, but having them early on and often is a huge deal; in fact, researchers at Kansas State University recently found that finance-related arguments are the biggest predictor of divorce.
"Don't give more attention to planning a wedding than your marriage; that's a recipe for marriage failure," said Berger. "Talk about who will work, how you'll distribute money within marriage and how things will be different if one spouse decides to be a stay-at-home parent."
9. The "I-hate-you-but-I-can't-live-without-you" couple.
Certain types are drawn to drama but constant fighting, breakups and reconciliations can't be the norm in any relationship, Gilbert said. It's simply unsustainable.
"These relationships are fueled by drama -- epic fights, affairs, sex-fueled reconciliations," she said. "Usually, the two people are attention-seeking individuals and choose to overlook their fundamental incompatibility because they’re addicted to intensity."
When the relationship finally does end, it's usually because one partner tires of the routine and dramatically makes their exit, "much to the relief of friends and family!" Gilbert said.