How to get through a break-up

I am struggling today. I am on day 2 of being broken up with my narcissist ex boyfriend of 2 years. This came after months of me feeling ready to call it quits and struggling with how to end things between us. The problem is I already miss him soooo much that it hurts. I cannot stop thinking about him and still wonder about his potential (which is what I am aware that I fell in love with). I know that he would take me back in a heartbeat, as he didn’t want us to end. I know that if I hope to move on with my life successfully I need to keep this man out of my life. Where is the relief I was hoping to feel?! All I feel is sadness, grief and confusion. I don’t want to keep the relationship going, but it is like I want to fill this longing inside of me in any way possible. It hurts and it’s miserable. I’m so scared I will reach out to him, and that is the last thing I want. Help me to stay strong.

C – Breaking-up with my partner
T – I wonder if I was too hasty ending things
F – Confused/sad
A – Stalk him on social media, think about him all the time, resist reaching out (but barely), question the ending, rose colored glasses about everything that wasn’t working in our relationship, wonder if he can actually change, question everything!
R – self-doubt confirmed?