Repeatedly throughout my life, when I’ve met someone who had a particularly pronounced intolerance, for example against hypocrites or procrastinators or conceited personalities, it would turn out that one of that person’s own greatest character flaws would be that exact thing.
I don’t know why there is a connection but I’m certain that there is a connection, and being aware of it can help in navigating relationships. If someone I do not know well expresses a personality or cultural annoyance, I recognize that they are likely to exhibit this same behavior at a later time and can prepare for it.
Similarly, if I find myself becoming frustrated or annoyed by someone else’s character flaw, I first ask myself if it’s my own weakness in that area that is frustrating me, or something close to it. In those cases, sometimes by determining how to improve myself I can improve life for the other person as well.