He said I should be thankful that I met him, that we taught each other some things. What he taught me is how to be alone. Because never ever before I met him I felt so alone.
As a kid I was a loner, always stuck in my head daydreaming, identifying problems and designing solutions. I use to hide away in my mind from others, because there was no use in communicating if I were misunderstood. My body was there, but my mind was wandering in the infinite universe that is imagination. It was great, but it was still lonely. Then I grew up and I started leaving my mind sanctuary from time to time, because reality was pulling me in. But when I needed to escape and my sanctuary was always there.
Then I met him and I really, really wanted to stay close to him in reality. But he hurt me, he misunderstood me, so I began going back to my sanctuary again and again and again. Then he left. My link to reality disappeared. You would think that this would leave me forever in my sanctuary, but for a while it was exactly the opposite.
Then things started to go back to normal. I went back to my sanctuary, I rebuilt the walls. I made them thicker, higher, stronger. It was still lonely, but it did not bother me anymore. I am strong you see, I fear nothing. I thought I feared being alone. But the thing I feared the most, is feeling alone with someone by my side. Feeling alone when you are actually alone is just natural. Like feeling hungry because you did not eat.
So yeah, I should thank him. He taught me how to be alone. He helped me accept that I will always be alone, in my mind or outside of it. And you should not fear the things that you have no power to change.