I have been thinking about this at great length, especially with the fresh turnover into a new year. Who do you have an easier time allowing to take advantage of you, your friends and family - or strangers? It could be separated even further - into friends OR family OR strangers too.
Sometimes it's just little things, but little things can add up and turn into big resentment. When is it time to say something, soon after it happens, so you can try to prevent it from happening again, or should you wait and see if it was just a fluke? Do you alter your behavior and say something right away to SOME people, not say ANYTHING to others?
I see so many people not want to offend anybody, often to the risk of themselves. Instead of saying something to another person, they keep their irritation to themselves and it builds up and later they explode for 'no reason' on someone else over something stupid that may not even be related. I think it's time for a social experiment :)