Today was a bad day and now I feel very down?

I don't know about anyone else, but I get days when everyone is mean to me and today was one of them days. At work everyone was being snappy and when I got home my room mate was being a *****. I'm a sensitive person and I sometimes become close to tears when people are nasty to me. I'm only nasty to people if they do something bad to me, I could never be nasty to someone for no reason. I feel that I am too much of a nice person and it is getting me down :( I don't want to change who I am, I wish there were more nicer people in this world.