Relationships can last a lifetime. Or they can sizzle out after a hot and heavy month.

But if you've been dating someone for a while and still don't really know if they're worth your time, new research from the University of Utah can shed some light on your situation.

Thing is, breaking up is difficult because relationships have layers of complicated pros and cons. Some are deal-breakers, some are tolerable, and some make it next-to-impossible to cut things loose.

In an attempt to peel some of those layers back, Utah researchers talked to people who were on the cusp of a breakup and trying to decide what to do. They asked men and women were asked open-ended questions about their reasons for wanting to stay and leave their relationship. They arrived at 27 reasons that support staying in a relationship, and 23 reasons people give for wanting to leave.

In the second phase of the study, researchers turned those 50 factors into a questionnaire and presented it to another group of people who were trying to decide whether to end a long-term relationship (on average, two years) or their marriage (roughly nine years).

For the most part, couples who were dating said they'd stay because of more positive reasons—they "loved their partner's personality," they felt "a strong emotional closeness," they "really enjoyed being together." Married couples, however, tended to think along the lines of "constraints"—they'd "invested many years in the relationship," they identified family responsibilities and logistical barriers (kids to worry about), and they were "afraid of the unknown." Even for people in unsatisfying relationships, the notion of starting new again was terrifying for most people.

"What was most interesting to me was how ambivalent people felt about their relationships," lead study author Samantha Joel, Ph.D., said in a press release. "They felt really torn. Breaking up can be a really difficult decision. You can look at a relationship from outside and say 'you have some really unsolvable problems, you should break up' but from the inside that is a really difficult thing to do and the longer you've been in a relationship, the harder it seems to be." 

Here are the top reasons, ranked by importance:

Top 27 reasons to stay in a relationship

  1. Emotional intimacy
  2. Emotional investment
  3. Family duty
  4. Partner's personality
  5. Enjoyment
  6. Emotional security
  7. Physical intimacy
  8. Financial benefits
  9. Compatibility
  10. Concern for partner
  11. Optimism
  12. Validation
  13. Dependence
  14. Attraction
  15. General satisfaction
  16. Comparison of alternatives (fear of not finding/having someone else)
  17. Logistical barriers (shared bank accounts)
  18. Fear of uncertainty
  19. Social connections
  20. Comfort
  21. Habituation (you're reluctant to change and content with the way things are)
  22. Companionship
  23. Long-term orientation (you can see having a future together)
  24. Long-term prospects (she'd make a good wife; you both want kids)
  25. Social pressure
  26. Self-improvement
  27. Social status (popularity and prestige)

Top 23 reasons people end relationships

  1. Partner's personality (flaws)
  2. Breach of trust (cheating)
  3. Partner withdrawal
  4. External reason (she moved half-way across the country)
  5. Physical distance
  6. Conflict (constant fighting)
  7. Incompatibility
  8. Emotional distance
  9. Lack of validation
  10. Lack of financial benefits
  11. Lack of enjoyment
  12. Problems with long-term prospects
  13. General dissatisfaction
  14. Inequity (one person is putting more of an effort; the relationship is one-sided)
  15. Social consequences (your relationship is hurting your friendships)
  16. Dealbreaker (physical abuse, psychological issues)
  17. Loss of attraction
  18. Too demanding
  19. Alternate partner (someone fell in love with another person)
  20. Pursuit of other opportunities
  21. Uncomfortable with commitment
  22. Hindering self-improvement (bad influence)
  23. Violation of expectations

"Humans fall in love for a reason," Joel said. "From an evolutionary perspective, for our ancestors finding a partner may have been more important than finding the right partner. It might be easier to get into relationships than to get back out of them."