Sorry for your loss.
It's terrible, I know.
My cat had cancer, and even though she wasn't dying there and then, her quality of life was poor and it had the potential to cause her some neurological problems in the future.
There's not much I can say to help you get over it "here and now". You need to grieve for the loss of your pal, and part of that just takes time.
At first, I know you will question yourself.. Did you make the right decision, did you spend enough time with the cat, did you say you love it.. goodbye. I did the same thing but after a week or two those questions that made me feel like I'd been kicked in the stomach sort of.. Went away.. And I started to just remember the good times.
And that's the important part! Remember when your cat was happy, remember the life you provided them, because god knows what they would have had WITHOUT you.
And don't doubt your decision(s) - I know this is hard to say now, but this is the way I look at it. Others may doubt the choices you make, but the decision is personal to you, and when you feel that you HAVE to do it, you have made the RIGHT choice.
Saying that, I am terribly sorry to hear of what happened to your little Merlin.
P.S. Me and my Mum heard phantom meows for a while when we had our cat PTS. Real or not.. It's comforting. And yeah, spooky

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