TL;DR: people grow distant. But there's more.
Relationships end for seemingly many varied reasons. But studies found one common factor: one or both partners exhibited a state of silent fight or flight mode (with increased heart rates, perspiration, and stress hormones) in each other's presence.
This means that emotionally, they didn't feel safe.
Safety is the foundational bedrock for intimacy (which is not necessarily sex but closeness), and when couples lose safety, they get distant, and distance is the core reason for most endings.
What makes people feel unsafe emotionally? Here are some examples of things we can do without even realizing it that can make people shut down (and this can happen whether the behavior is displayed directly to, or witnessed by partners -- all can cause damage):
- Criticism: How things are worded can mean a big difference in how they're received. Criticism tends to be a sweeping generality and includes judgments about character, habits, and other personal qualities. The antidote is to complain rather than criticize. A complaint addresses a specific issue with the goal of problem-solving. For example, a criticism can be, "You never clean up after yourself!" or "You're a slob!!" "Never" is a strong word and saying this can put someone on the defensive, as can labelling someone. Neither are helpful and actually hinder the desired outcome, which is to solve a problem. It's Better to say something like, "Can we talk about a better solution to keeping things clean? I feel like I've been doing more of the share and I really want that to feel more equal."
- Contempt: This communicates disgust and is particularly dangerous over time. It can seem playful but it's actually a disrespectful judgment and can end up making someone feel devalued. For example, a contemptuous remark could be: "He cannot cook to save his life!" Better to say: "He doesn't enjoy cooking as much as me but we both find eating out fun!"
- Eye-rolling: Eye-rolling is a contemptuous bodily signal and is as effective as words for making people feel crummy. It also makes people feel devalued and defensive (most of the things in this bulleted list do and can often elicit sharp responses or slumped, downtrodden manner).
- Making fun: It can be common to think you're being playful but poking fun can still breed disrespect and can make people feel devalued which builds over time. For example: "Haha, your clothes are so ratty! Not like you even notice." Better to say, "That's not my favorite shirt on you, what do you think of wearing this one for me instead? I love it on you."
- Disparaging comments: These can also can make people feel less appreciated. For example, a comment like "Wow, you can really eat!! You'll have to jog home to burn all that off!" is insulting. Judgments are better off not leaving your lips. When is something a judgment and not a comment? A judgment is anything that places the speaker in a role of "better than" the receiver. It distorts the power balance between peers and even if not consciously realized, is felt and thus is distancing. "Your music is stupid," "you don't fold towels correctly," "the movies you like are dumb," etc. -- all are shaming and can make people feel bad about their taste and choices. It's okay to not like the same things as each other, or have ideas of systems that work well -- perhaps the towels really do fit in the closet better if done a certain way. You can communicate respect even along with disagreement or wishes for change. "Oh, that's not for me," or "I really like it when the towels are folded a particular way because they fit a little better, can I show you? Would you be willing to give it a try?" (Note, it may take a while to change habits so be patient.)
- Disrespect: For example: "There she goes again!!" Better: "Are you having trouble with that? Do you want my help?"
- Frustration: Even if not pointed right at a person, frustration can still cause stress in others. The brain is unconsciously primed to pick up threat cues in the environment and a volatile person is not in control. Lack of control makes safety alarms go off. Look at a dog next time someone slams a door -- that's the reaction happening inside most folks even if they've learned to conceal their discomfort. Studies of those exhibiting stony exteriors during an argument found distress signals like heart rate and cortisol production very high. Frustration directly pointed at a person, however, can cross lines into abusive behavior. It doesn't matter if the frustrated person "can't help it" -- abuse is never justified or deserved even if it's the result of not being able to manage strong emotions well. The need for better emotion regulation is not something to be ashamed of but instead feel positive that much can be done to build "muscles" over time and get much stronger & better at handling emotions. Learn more.
- Avoiding difficult subjects: It can seem like it's better to just not talk about something and avoid frustration or an intense reaction but paradoxically, not discussing topics increases distance. Problems can't be solved if they're not aired. However, it can be hard to bring something up when an anticipated reaction is unpleasant, or if hope has been loss that change can actually happen, especially if it's been brought up but not enough action has manifested yet. Writing it out might help, if talking is difficult, as can counseling. (The right counselor can make a huge difference -- look for someone either well-versed in the Gottman method or in Emotionally Focused Therapy (EFT) or get recommendations from folks you trust.) If your partner won't go to counseling with you, go alone. It will still help.
- Lack of self-care (over an extended time): This can be a surprising factor but caretaking takes lots of energy. It's hard enough to get adequate sleep ourselves let alone make sure someone else does too (or has whatever else they need) no matter how much we love them. Anyone who has been in a relationship with a partner who refused to seek treatment for medical or mental health difficulties understands this, as well as parents. We have no control over others so cannot make sure they get their needs met, only they can. It can be exhausting to take on the role long-term to making sure someone else has what they need and this encompasses all needs including emotional fulfillment, resources like food, finances, or things, medical care, mobility, etc. Self-care is the best gift we can give those around us.
- Positives need to balance negatives: For every negative interaction people have, Dr. Gottman found that 6 positive interactions are needed simply to cancel it out. Erasing negativity is not a 1:1 ratio but a 1:6 ratio. Getting to actual happiness takes even more work -- 20 positive interactions for every negative one so the ratio is 1:20! A positive interaction can be small -- making someone feel valued, appreciated, thanking them and recognizing their efforts, etc. (Whatever their "love language" is, feed it.)
- This all applies not only to romantic relationships but all relationships -- colleagues, friends, family, loved ones, neighbors. Treating people with respect is key for connection.
If you can follow Dr. Duana Welch's advice to "find and be someone kind and respectful" that will go a long way toward relationship happiness.
Sometimes distance can evolve from factors in a person's background that have less to do with the relationship dynamic and more with individual needs for connection or safety. That is for another post, as well as the importance and challenges of skill development for folks with neuro-atypical brains like ADHD, trauma, etc. but communication skills and habits learned in childhood do not necessarily encompass all we now understand about good communication and awareness can really help.
Dr. Gottman, renowned for his relationship research, talks more about The Four Horsemen of the Apocalypse, or some of the factors that can unravel the sense of emotional safety in a relationship.
A final excellent read is Al Turtle's article on safety and the lizard brain. Enjoy!