Almost nobody leaves over one bad night. They leave after a long quiet stretch where nothing was obviously wrong, and nothing was quite right either.
Nobody notices the evening the conversation got shorter, or the month you stopped asking how her day went because you already knew the answer. Every one of those days is forgivable on its own. That is exactly the problem. There is never a day worth raising, so nothing gets raised, and a hundred nothing-days become a distance neither of you chose.
Memory keeps highlights, not averages. Ask either of you how the last six months went and the answer will be shaped by the last good weekend or the last bad Tuesday. You are both being honest. You are both describing a mood rather than a year.
That is why two people remember the same months so differently, and why arguing about the past never settles anything.
Not a diary. Not a case file. Just a small honest mark on the same few things every night: did we talk properly, did I feel wanted, did we get any time that was actually ours. Sixty seconds, then put the phone down.
Thirty of those in a row will tell you something no conversation will, because it is a record instead of a feeling.
Usually one thing sliding while everything else holds steady. That is good news. "This one thing has been off since spring" is something you can act on. "We are drifting" is not.
Change one small ordinary thing, keep marking the days, and watch whether the floor comes back up. Two weeks is normally enough to know whether it is working.
The couples who last are not the ones with fewer bad weeks. They are the ones who noticed the bad weeks while they were still weeks.
Nobody drifts on purpose. You only have to look up more often than once a year.
Read the other sides: his side · her side
Disclaimer: Personal perspectives only, plain old-fashioned thinking about what keeps people together, not professional advice and not endorsed by any organization; if anything at home feels unsafe, please talk to someone you trust.