Why is so hard to get over Him or Her

We all remember our past relationships, good or bad memories, and sometimes laugh about them. But there are some relationships we can't ever move on from. Why is that? This can be frustrating. Here you are trying to see new people, but can't get this person out of your head, your dreams and thoughts, everywhere you go you see something that reminds you of them. Doesn't matter if you guys dated for a long time, couple months or perhaps was an occasional thing. This particular person touched your very inner self like no other.
Here I'll give you a couple reasons why you can't get over them.

1. You miss the way they made you feel.
   Here you are in an emotional rollercoaster, going back and forth, should I reach out or should I wait?. One thing you can't ignore is the way you felt with them. For the first time in your life, you meet someone that makes you feel comfortable, free, at home, important and more importantly you feel yourself with them like you can do anything and not pretend.

2. You think you will never meet anyone like them
   It was love at first sight, you guys click and it was like magic. Not only the connection between both was intense, the more you get to know them, the more you find how similar you both are. And let's not forget the fireworks in the bedroom!!, damn, is at this moment when you realize this person is special. And now you are perhaps meeting new people and you make the huge mistake of comparing them with the one you love, and yes I said it, Love because at this moment is when you realize what are your true feelings for them.

3. Everything reminds you of them
   Maybe its a song, a place, a tv show, etc; but you still can't shake this feeling out.

4. You realize that its Love and not infatuation
   The more you get to know them, the more you want them, the more you need them in your life, you want to share everything with them. They make you smile, they make you happy. Now you know what you feel and is something new, you never felt this way before, and letting go of them hurts like crazy because you don't know if you ever will find love like this.

Advice
Love comes many times in our lifetime, but loving someone doesn't mean you are in Love with them. With that said, if you happen to meet a person that makes you feel you, please, don't let go! you might regret it forever.