Why is it so hard to let go of the pain the memories and the hurt that feels eternal and inescapable?

I have went days keeping my emotions under control but the feeling of sadness is inescapable it's like I was not meant to escape it or avoid it in life. It is hell for me. It is a problem for me I am trying to do hw but the feeling is just growing stronger I mean I don't want to face it I just went to let it all go but it keeps coming up again in my obsessive brain, I want to cry in a fetal position on my bed and I also just want to self-medicate with pills to relax my mind...I can't forget this guy and the abandonment and rejection I had to go through. AGAIN.

Sometimes I think if the guys who have abandoned me in the past were mean guys that ended up leaving me it would all be better and make more sense but that is not the case. These guys all seemed perfect and kind and I didn't think they would ever do me wrong. As much as I wish I could MOVE ON I CAN'T BUT I don't want to replace a guy with another I want to be okay with just being with myself. Happy with me.

How can I deal with these feelings? If any one has any ideas or positive reinforcements let me know please I am in a dire need of help right now because I don't want to fall....I have made progress in staying content and optimistic but I am having problems at the moment. Please write me if you have anything to say.

Thanks in advance