How do I exist without her?

I had the most beautiful girl in the world for the past 10 years. Her name was Sage, and she was placed on my lap by her mother the minute she was born, and now I’ve lost her. My husband heard her yowling while I was at work and saw she couldn’t move her hind legs and rushed her to the emergency vet, I rushed there from work as well. When I got there they already had her in the back and the vet came to speak with us and told us that Sage had Saddle Thrombus, and it was extremely bad. The vet explained to us that her chance of survival was minuscule and that it would be constant pain until another clot formed. We called our primary vet and they told us the same thing, the only option for our baby to not be in pain was to let her go. We spent time with her there, she was staring into my eyes like she always did, and after an hour after constant forehead kisses and me telling her how much I loved her through my sobbing, she turned her head away and laid it on my hands and we knew she knew that we couldn’t protect her from this and she was ready. I wished I could hold her in my arms but knew that moving her would cause unneeded pain, so I had to just hold her head in my hands as she took her last breath. I’m a very spiritual person, and I believe she will come back to me again, but how am I supposed to survive this pain? The only thing keeping me going is my husband and our other cat, Odin. But my heart breaks every morning I wake up and see Odin lying on him but Sage isn’t on me like she always was. Sage was everything to me, she’s always been with me, I’ve been holding the blanket she liked to sleep on because it still smells like her. It feels like the most important part of my soul has been ripped out of my body. Has anyone else had this sudden loss? How did you handle your grief? Did they come back, and how soon? I really don’t know how I’m going to go on, I can barely eat or drink, I just feel so empty.