Imagine everyone doing it: that is the pause I try before giving myself permission to make an exception.
Before I give myself permission to do something, I try a question: what if everyone did this? It becomes harder to excuse a choice when I am no longer the special exception.
I find it useful as a pause before a decision. It is a prompt for reflection, not a machine that produces the right answer to every situation.
Suppose you are tempted to break an agreement because keeping it has become inconvenient. Instead of asking only whether you could get away with it, ask what would happen if everyone treated that agreement the same way.
Be precise about the action you are examining. There is a difference between changing a commitment openly with the people involved and quietly ignoring it. A vague label can hide the part of the decision that matters.
After the thought experiment, return to the actual situation. Who would be affected? What have they been told? Is there information you are missing or a responsibility you have not considered?
People have different circumstances, and imagining one rule applied to everyone will not resolve every conflict. It can still reveal when your reasoning depends on giving yourself permission you would refuse others. That is a useful moment to stop, reconsider and choose a way forward you can explain honestly.