What's kind vs What's fair

I'm driving home from class today. And it's my long day so I've been at it since 5 this morning and just getting home 12 hours later. So my mind is racing with wonder with what I will find in the mailbox as I'm STILL waiting on my acceptance letter. And the class I had just finished I was asked to teach at the last minute and that was playing in my mind like a looped movie. And I met a boy on the train so I was thinking about how bazaar our conversation was. I'm rambling, but my point is that my mind was racing and all I wanted to do was to be home and think about mindless things like how many of Jenny's Halloween cookies would be left for me to eat for dinner. I approached a long line of traffic at the train tracks where I wait to turn left. As I'm waiting, a car pulls up from the parking lot on my right as if to pull out in front of me. I start running the scenarios in my mind.

How old is this car? Will it be able to keep up the pace I had been driving? How old is the driver? Will he be too cautious or will he just bust out and turn? How much time will I lose if I let him in? Where is he going? Is it really important that he is in line in front of me instead of behind me? I found myself asking more questions than my conscious thoughts were able to answer in the 15 seconds I was given to make the decision. Then, just as the cars ahead began moving forward, it was time... I let him in! I smiled proudly at my decision to "do the right thing" and show kindness to a stranger. Grinning ear to ear actually. Wow! That was really nice. I raised my hand to wave "You're welcome!" Whoa, wait a second. Not even so much as a glance at me to say thank you. It was just expected.

After being disturbed about this for almost a whole minute, I wondered... Do we do kind things because we expect some sort of reward for our kindness? Or do we do kind things because that is the way that our character manifests itself in our outward lives?