I’m very sorry to hear of your cat’s passing. 12 is getting up there for cats although I did have a tabby that lived to be 24 yrs.
I just had to put down my 21-year old cat last week - it was very hard to do but he started deteriorating rapidly and it was painful to watch. I kept hoping he would just pass away in his sleep, but when it got to the point when he could not even walk without falling over, could not eat even the soft mashed up food I was giving him and a whole host of other problems, I could just not stand to see him suffer anymore. He was quite the curmudgeon the last few years but I loved him dearly. 21 years is a long time as a companion and I just don’t think getting another cat would work for me, though.