Whether a relationship is good or not depends mainly on how you feel within it, not on your partner’s attributes

Cost: There is no monetary cost, nor does it require much time. The real challenge lies in shifting your perspective: put aside your checklist of ideal partner traits and instead focus on how you interact with each other.
In plain terms: The best indicator of a healthy relationship is your own feelings toward it, not your partner’s qualifications. For instance, whether you perceive your partner as attentive and appreciative of you, or how often you argue. Your personal feelings carry two to four times more weight than what your partner says about the relationship. However, no questionnaire can reliably predict whether the relationship will improve or deteriorate over time.
Benefit: A machine learning analysis of data from 29 laboratories and 43 longitudinal paired datasets — meaning data collected from the same couples over time — found that the strongest predictors of relationship quality all stem from each partner’s own perceptions of the relationship: their sense of their partner’s commitment, appreciation, sexual satisfaction, and contentment; as well as the frequency of conflicts. Among individual-level factors, life satisfaction, negative emotions, depression, and attachment styles (both avoidant and anxious) also play a role. At the start of these studies, these relationship-related factors could explain up to 45% of the variation in relationship quality between different couples; by the end of the studies, this figure dropped to 18%. Crucially, the predictive power of self-reported relationship perceptions is two to four times greater than that of perceptions reported by partners. Adding individual differences and partner-reported data to self-reported perceptions yields no additional predictive value.
Evidence grade: A
Sources:Joel S, Eastwick PW, Allison CJ, et al. (2020). Machine learning uncovers the most robust self-report predictors of relationship quality across 43 longitudinal couples studies. Proceedings of the National Academy of Sciences, 117(32), 19061-19071. https://doi.org/10.1073/pnas.1917036117
Notes: This same research also found that no set of self-reported questionnaire items can reliably forecast whether a relationship will improve or worsen during the study period. Therefore, while gauging your own feelings about the relationship is far more accurate than cross-checking your partner against a checklist of ideal traits, it still cannot predict the relationship’s future trajectory. For a deeper look at how relationship quality ties to physical health, see Section 17 of this chapter, which frames relationship health as a component of overall well-being.