<human>: Give me a shortened version of the text

Sorry if this is long,

We started dating when I was 20 and she was 18. We instantly clicked, fell in love and became lovers and best friends. We did everything together and basically became one person. I felt amazing, no girl ever loved me as hard as she did. We dated through college and a few years after we graduated we traveled a bit and then I proposed to her. It was the happiest time of my life.

A few months after we got engaged she stared to become distant. I let it go and just ignored it for a while. After this went on for a few weeks I asked her, is everything okay? It turns out, that when her ex bf found out we were engaged, he contacted her and it brought back old feelings for her. She told me she loved us both. She went to therapy for this and it did nothing. I stayed by her side because I wasn't willing to let her go. I loved her too much to walk away. A month later she calls me and says "we need to talk" we spoke for a bit and she says, I can't do this anymore. She gives back the ring and I leave.

I was in a state of shock and so confused after this. How could se throw away all of this? All of the memories, wedding plans, our future? 
It really didn't hit me at first, now after 5 months, my depression is settling in. I have lost motivation at work, I don't want to go out, I tried dating other people but I hate it. I can't stop comparing every girl to her. I think about her from the moment I wake to the second I fall asleep. I still dream about her from time to time. She was smart, funny, beautiful and had a great family. 

I get emails from her every once and while, asking how i am and that she made a mistake and regrets everything.

How do people deal? My life feels like it has no meaning anymore. I feel like a zombie that just goes to work and the gym. I go out with friends and laugh but at the end of the day a part of me is gone.

Advice?

Thank you!
<bot>: Ex Fiance broke off the engagement, after 6 years together. Im depressed, unmotivated, emotionally destroyed, and can't stop thinking of her.