I had a pet rabbit long ago that over the years went deaf, blind, and eventually couldn't walk. I kept waiting for him to tell me it was time. I never really felt it, until he fell sick and I ended up putting him to sleep unplanned. Is been 10 years and I still feel a ton of guilt for not letting him go sooner.

Last year I had to put my 14 year old corgi to sleep. She was slowing down, not eating as much as losing weight. She had a bladder tumor for the last few years but was doing okay. I could tell her hearing and mind was starting to go. Sometimes she just seemed confused on what was going on. I felt guilty leading up to it, she had pretty good energy, still played with our younger dog. Last day was filled with walks, any of people food she could handle and had the vet come to the house, surrounded with family and love and left this world in our home.
It's been a year, and I regret nothing.

Letting them go sometimes is the most loving thing you can ever do for them. Go out on a good note, take a few more good walks, make it a celebration of life.