For months, you’ve been handling disagreements differently.
You still get upset, but you don’t immediately assume the relationship is in danger. You can listen longer. You recover more quickly. Sometimes you disagree without thinking much about it afterward.
Then life gets difficult. You stop sleeping well. Work becomes demanding. Someone in your family becomes ill. You’re tired most of the time.
One evening, someone disagrees with you and the old reaction comes back. You become defensive. You hear criticism where none was intended. Hours later, you are still thinking about the conversation.
It can feel as though the change disappeared.
But change does not happen independently of conditions. If greater capacity, different relationships, repeated new experiences, or a more manageable life helped something different become possible, a substantial change in those conditions may affect what remains available.
That does not necessarily mean you are back where you started. Perhaps the reaction returns, but it takes more difficult conditions to bring it out. Perhaps you notice it sooner. Perhaps it lasts an evening instead of three days. When the difficult period passes, the newer way of responding returns more readily than it once would have.
Durability does not have to mean that an old response can never happen again. It can mean that a different response has become available under more conditions.
At first, something new may appear only when circumstances are favorable. You can speak up with someone you trust but not with someone who intimidates you. You can tolerate frustration when you are rested but not when you are exhausted. You can respond differently when you have time to think but not when something happens quickly.
With repeated experience, that range can widen. What once required unusually favorable conditions may become possible in ordinary ones. What once disappeared under modest strain may remain available until the strain becomes much greater.
The conditions around the change may also begin to change. A different way of responding can alter a relationship. Greater capacity can make choices possible that preserve capacity. More reliable sleep can affect how the next day is lived. A life that becomes somewhat more manageable may make it easier to keep living in ways that preserve that manageability.
The consequences of change can become conditions that help sustain further change.
Even then, no way of functioning becomes completely independent of conditions. Severe illness, loss, exhaustion, danger, prolonged uncertainty, or other major changes can narrow what is available again.
Lasting change does not require becoming unaffected by any of that. It means that something different has become more available, under more conditions, and more capable of returning when difficult conditions temporarily make it harder to reach.