My partner and I are fully loyal to one another

Loyalty gets imagined as a test, some dramatic moment where you either hold the line or you don't. It is almost never that.

It is how you speak about someone when they are not in the room. Whether their bad week becomes an anecdote at the pub. Whether you defend them to your own mother. Whether a joke at their expense gets left unchallenged because challenging it would spoil the evening.

Those choices come round weekly and nobody records them. Full loyalty is the accumulation, and it is being practised long before anything tests it.