Every time. I feel guilty every time.
And I'm old, so I've put quite a few down.
I wrestle with the decision every time, too. I take it very seriously. I hate to see them suffer, but I always wonder what gives me the right to decide that their life is so miserable that it should end.
I'm sure there's some guy living in the Hamptons who would look at my life and say it wasn't worth living.
But I love my pets, and am a responsible pet owner, and when it's time, I do it, and just deal with the guilt along with the grief. It's hard.
But there is always another animal with a sad story just waiting for a chance at a good home, if your house is empty, head on out to the pound and save one.
So don't second guess it. You loved your cat, your cat knew it. You did what you knew was best.
Grief comes in many ways.