Let someone go first

Whenever I take the public transportation, I always let someone go first. I took a bus on my home last night and people were hurriedly running to take the bus and I just took my time to let people get in first.
One of the most memorable time of letting someone go first was when I opened the door for a grandmother coming towards the door, and she gave me a big wide smile saying thank you to me.
Those little moments really makes me keep on doing this.