How you ever been deeply hurt by someone?

Yes. I was connecting with someone that I felt for. I thought we were having mutual feelings but apparently not. I was giving him lots of advice and positivity, which he needed and appreciated because he was facing a crisis.
Then I needed him. And he just started ignoring me. I haven't heard from him in months. No reasoning behind why he stopped talking to me, he just threw me away. Drained me of my energy and tossed me aside. I have so much anger built up that I don't know if I should let it go or not.