My partner and I feel comfortable and safe with each other

One test: can you say something badly? Not cruelly, just clumsily, half-formed, in the wrong order, and trust that the worst possible reading of it won't be the one that sticks.

Safe rooms are the ones where sentences get repaired rather than filed. That is most of it. Not the absence of conflict but the absence of a permanent record.

Comfortable has a poor reputation, as though it were the first stage of decline. Plenty of people burn through years of intensity looking for a room they could finally exhale in. Being able to be dull together is not a failure. It is the whole point of a shelter.