history: Any time i let someone out in front of me in traffic and they don't wave i get angry. It seems every day in traffic i'll let someone out and don't get a wave or anything. Thats the worst when you do something for someone and they dont even appear to care! 
current: No doubt, but i always try to do what i would want someone to do for me.
next: Same! Two wrongs never make a right.  You are doing the right thing. 