Am I a terrible person having to euthanize my cat?

I am feeling terrible.

I rescue and foster stray cats. One of the stray mothers gave birth to this kitten six months ago. He got so attached to me, didn't get any home for him. He was living with me.

Suddenly 15 days ago both of his hind legs got paralyzed, went to the vet, did an X-ray, and the report come normal, even after many other tests vet didn't find anything. But anyways gave some medicines. I was giving them for 15 days, giving other care like baths and warm massages but the situation didn't improve. He was suffering and in pain all the time. So had to euthanize him.

I am deeply feeling remorse, drenched in his memories.

Am I a terrible person having to euthanize my cat?
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