A well-known story: along the path of the Prophet Muhammad (s) lived a woman who often threw rubbish in his way. The Prophet did not get angry and simply walked on.
One day the rubbish was gone. The Prophet asked about the woman and learned that she was ill. He visited her and kindly asked how she was. She was so touched by his goodness that she felt ashamed of what she had done.
What we learn: kindness can change hearts – even when someone has not been nice to us.