In the quote above George Saunders reminds us that being passive or being a witness to something that you could have helped change is equivalent to not being a good person. Okay, maybe that's not exactly what he's saying but it definitely makes you think about all the times where you could have done something but didn't.
I think I can assume that we've all had moments like these. Where we witness an injustice -- no matter how big or small -- and we continue to go about our day. We try to rationalize and say that we are busy or that someone else will do the good thing that you are just too busy to do.
You won't stop the car when you see someone who needs help. You won't buy that homeless woman a meal. And you won't take time out of your day to send your Mother flowers even though you said you would 6 months ago. I think these are the failures of kindness Saunders is referring to.
So maybe you know, you should call your mom/dad/brother/friend. Tell them you love them. Or the next time you see a guy on the street who is hungry and cold you'll buy him a bagel and coffee. And maybe when your co-worker is leaving the room every couple of minutes to cry, you'll ask them what's wrong instead of smile awkwardly at them until the work day is over.