Why Do People Treat Others Wrongly

Okay I am just going to say it.... Some people are just rude. I just not understand it,that when I do something out of the kindness of my heart to help some one they get mad and act like a child. I mean what happened was not my fault, come on when you ring someones doorbell 6 times and knock really hard on their door about 6 times and wait for 10 minutes. What am I suppose to do stand outside their door all day. I am sorry but I had things to do. Now this person is mad at me because she had to find another way to pick up her kids. See we use this persons mom's van when when have to pick up this persons 2 kids plus our 2 girls. I am sorry but we can not fit all 4 kids in our car. We have been doing this for over a month to help this person out, because we know how hard things can be. well I am sorry no more I am tired up helping people and then they get mad at me and not respond to any of my emails or any thing. I am a good person and I go out of my way to help people, but i am so so tired of getting treated like I am worthless and because I am not.