When your grown up you have to get used to others who aren't

Why do some people get angry or criticize unreasonably? I have given more than desired time contemplating. The best was, he must be frustrated with someone else or something and needed a person to lash out on to feel better. Poor me! Or on the other hand maybe he is jealous of my ideas and way of life. This is the best I could come up with to take it with a grain of salt. It is useless to waste time pouting on people who wish to reneges on promises for disappointment. When your grown up you have to get used to others who aren't.