If I said it once, I don't care if I say it again, be nice to people. No matter what. If someone doesn't hold the door open, don't embrace that person's anger, take it and let it die by giving love to the person behind you. Hold the door open for them. With a smile.
Don't let mean people break you. It's not worth it. The fact that they are mean or rude has nothing to do with you, almost always. Don't internalize it. Don't worry about what you did wrong.
Be kind. Do the right thing. Love a little. What's the worst that could happen?
