I am so sorry for you for what you are going through and considering the fact that you want to push through it despite it being so hard shows such a strength and courage within yourself. I admire that.
I'm trying so hard thinking so deep within myself what I would do during a rough breakup (because yeah, I do not handle those quite very well either).
Maybe try to look back in hindsight and think of all the red flags you have missed in this person. Think of all of his worst qualities. And also if possible, try as hard as you can to seperate yourself from him physically. Initiate no contact because continuing to speak and have anything to do with him is only going to keep those wounds fresh.
If you believe you have truly tried your best and hardest in this relationship from your end, then that is all the reason to be able to let go knowing that you tried your best. I know, much easier said than done.
Write in a journal all your feelings, scream, cry, look deep within the mirror at yourself and remember the reasons why you are choosing to keep going. Nurture yourself. Take deep breaths. Take things moment by moment. Go out for walks. Make a list of all your best qualities. Maybe make art or poetry channeling your emotions in that fashion/regard. Make up a mini-funeral and create a eulogy mourning the ending of that relationship. Start a fire and burn the mementos/memories/photographs down. Write/compose an unsent letter to your ex expressing how you feel expressing your closure and speaking your peace (or lack of it)?
Talk to other people about the breakup so others can provide you some kind of special insight on the matter? There's an app I have used before called 7Cups. It's a free mental health chatting service to speak to trained non-judgmental, caring listeners.
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