I too am VERY impatient (family trait). However, I know what causes my impatience - my OCD perfectionism. In my mind, everything must be done “perfectly”. Anything that prevents that from happening is exasperating (even though I know there’s no such thing as “prefect”), which causes me to be anxious and very stressed (I know, I know, not healthy). It’s that stress and anxiety that make me impatient. It’s extremely hard to tolerate someone or something when you’re stressed (or, as I tell myself, “they’re being stupid”).