The flaw you spot fastest in other people is usually one you know from the inside.

Spotting a pattern needs a reference. You pick out defensiveness or showing off in a stranger within seconds because you have run the same program yourself and know its shape from the inside. That is not hypocrisy, it is how pattern matching works, though it does mean your sharpest judgements are often a kind of self-portrait.

Think of the trait that irritates you quickest in other people. Sit with the possibility that you do a quieter version of it. If you find one, you have been handed a piece of information nobody else could have given you.