Why it's easy to miss from inside the relationship
Each instance can be argued individually — 'this time is different because...' — which is exactly what makes a pattern of double standards hard to see without stepping back and looking at several instances side by side, not just the latest one.
The test that cuts through the individual excuses
Swap the roles mentally: if your partner did exactly what you're being criticized for, would the same standard apply to them? If the honest answer is no, that's the asymmetry, regardless of how the current instance gets explained.
Why double standards often hide inside otherwise reasonable rules
A rule can be legitimate in general — checking in while traveling, for example — and still be a double standard if it's only ever enforced in one direction, which is why the rule itself isn't always the problem; the asymmetry is.
How to raise it without it turning into tit-for-tat
Naming the specific pattern — 'I've noticed this rule only seems to apply to me' — tends to land better than demanding equal treatment as punishment, which keeps the conversation about fairness instead of about scorekeeping.
Not every difference in behavior is a double standard — people have different needs and different histories. The actual signal is a rule justified by 'because I said so' that wouldn't survive being applied the other way around.
Recognizing the pattern in general helps. Naming the one rule that only ever seems to apply to you is the harder, more useful thing to look at. Name that rule, in OLENRI