I am now hurt all over again :(

I cleaned out my email box. I found an email that hurt me and now I’m hurt all over again. I know that I was basically nothing to the other person because we met professionally… but I’m still hurt quite a lot. I was emotionally invested so now I am actually feeling heartbroken. I don’t know how others can be so cold. I’m now just as heartbroken as I was the first time that I got the email. It’s reopened the wound I closed and then refused to let hurt me by walking miles and keeping constantly busy.