Why is it so hard

Today, like any other day, my ex of 9 years was on my mind. I've been in relationships before, but never with a narcissist. I knew from the very beginning that there was something different about him and all my family and friends said he wasn't right, and of course they were right on the money. My question is this...why, when this man ripped me apart for years saying things on a daily basis to me like "you need to eat a salad," "your hair isn't long enough, you need to grow it" (WTF?), "your teeth aren't white enough," "why can't you look and dress more like her?", and there are many, many more, why do I still have feelings for him and miss him? We've been apart for 2 years and I just can't let go. Since we've been apart, he's had many girlfriends and I just ran into him and another girlfriend at the market. She was everything he said he never wanted - overweight, over processed "short" hair, etc. I just wanted to go over and punch him in the face and say "WTF???". This man drove my self esteem to the ground, I put on at least 50 lbs because I was so stressed and depressed when I was with him, but after all the years of dealing with someone who obviously loved himself more than he loved me, I just can't get him out of my mind. What do I do? I work many hours and go school part-time. I've been dating occasionally, but feel I'm really not ready for a relationship yet. Any advice would be greatly appreciated.