Being a Dog parent

I have failed as a mother. My baby dog Mac died on 14th September 2021. He was an Indian breed dog. It was going to be two months since he came into our lives. We nurtured him, cared for him, and loved him. I still blame myself, I don't know why. I feel like there is no meaning to my life, I couldn't save him. I used to wake up in the middle of the night to check if he is alright. If he did potty, I used to clean him and tuck him in a cozy warm cloth. We were supposed to take him on the bed once he became completely well. He had a face like a mouse. He liked to lie on my lap and sleep. Me, my brother and sister have faced trying times as parents of our older dog Uno, but Mac was a special case, he was partially paralyzed in his legs. He couldn't walk properly and he passed stools without him knowing it. I never complained about getting up in the  middle of the night or cleaning his urine and potty. I had always hoped that he would get well soon. Yesterday when we had to take the decision to euthanize him as the doctor said he may have rabies or canine distemper, I broke down. It broke my heart when he didn't recognize me. I couldn't imagine losing him. I thought about all the people whose closed ones died during Covid, without beds and oxygen. They might have questioned themselves, if they did everything to save their close ones, even if it wasn't really their fault. I couldn’t bear to look at his lifeless, pale body. This is the first time I lost someone close to me, and I still can't get a hold of reality, I can't believe he is gone. I questioned myself if we did the right thing. I felt guilty. I also felt stupid enough that I thought maybe because I don’t believe in God... Maybe not. I don't understand where I went wrong. We did everything or did we not. I didn't get to spend more time with him during his last day. If I knew I would have played with him more, I would have caressed him longer before leaving for office. I would have let him sleep in my lap for some more time. I wish when I return from office and ring the doorbell, you come running dragging your legs behind along with Uno, her tail wagging on your small face, you still making your way towards me.