It is time when you weigh-dispassionately-how much of a life the horse has taking into consideration pain, fear, etc. versus the mercy of a quick, painless sleep. It is hard to do, I know all too well.
We love our animals and sometimes we are in a way selfish that we want them to stay with us. But in the end the best way to express our love for our companions is to offer them a dignified end. I was just talking about this with a friend the other day, and said to her that it letting go is the bittersweet part of having animals as part of our lives.
I am thinking of you and your old friend.
We grow too soon old, and too late smart.