Holding My Best Friends Hand While He Was Put Down :(

I am 21 years old and I rescued Petey when he was just a puppy. He was a great Dane / Dalmatian mix and he was my best friend. He was the only one who was always there for me when I was sick or sad or going through a breakup with a boy, he always knew when I needed to bury my face in his neck and cry on him. Petey was a special dog... He had a problem with cats (ate 3 of ours neighbors) oops. He also was traumatized by thunder and lightening and would literally claw and chew his way out of any room or door just shredding each door frame in our house. We eventually got him tranquilizers from the vet which helped a little but he was such a big dog they didn't do much to him. He was the best dog ever and always wanted to play and get his ears scratched.. He would nuzzle his face in your legs until you rubbed his ears. As he got older the storm terrors started getting worse and he was tearing up the house. My mom was trying to get in the process of moving into another house and she knew she couldn't take Petey with her or he would just destroy it. One day I was off at college when my mom called and said we are putting Petey to sleep so you need to come home this weekend. I was absolutely devastated and cried for hours, I knew I was going to lose my best friend who has always been loyal to me. I knew I had to go with him to hold him while the vet put him to sleep. It broke my heart Because he wanted to play he thought he was going for a car ride to the park. It was not his time to go, he was perfectly healthy my mom was just tired of him destroying the house. I was holding him tight when the vet put the shot into his arm and he started to collapse in my arms but it wasn't strong enough because he was such a big dog. I was holding him in my arms watching him die right in front of my eyes. And then he was just gone. I gave him one last kiss on his big head where I loved to kiss him and had to walk away, I couldn't stand to watch them carry my baby away knowing he would never be back in my arms. It has been almost a year now and not a day goes by that I don't think about hi
. I was so depressed I had to get on depression/ anxiety pills because I literally feel like apart of me is missing. He was my best friend and I was his best friend. It was like no other bond I could have with anyone. I have his ashes spread in my backyard in the sun because that was his favorite place to be. I don't think the hole in my heart where he was will ever heal. I was glad I was with him in his last few minutes but I just know he was looking at me wondering what he did wrong. I pray to god that he wasnt in any pain and I can't wait for the day I see him again in heaven. I miss him so much we had an indescribable friendship