I am so sorry and I know exactly how much this hurts having escorted my Stanley on his final journey. No words can express what i wish I could, cyber hugs.
I am tearing up and my heart breaks as I understand this too well. I knew it was time, and poor dear was tired and sick. I'm sorry for your loss. My last ride with Ewok was something I'll never forget. Big hug. Words fail me. (I didn't want to write it earlier, but that vet article mentioned that they sometimes purr even when they are dying.)
I don't know the circumstances, but it sounds like you made the right decision. When My cats were suffering, I knew when the right time to let them go was, and believe me, they are feeling much better in the care and arms of G-d than they would be in any prolonged suffering.
My prayers and condolences are for and with you, have a blessed day.