That's a hard spot to be in but find peace knowing he had a great life with you.
My neighbor put his down just before Christmas. He couldn't bear watching him buried so I handled that part for him.
His horse was 33 and he'd had him 31 years. I did cut some hair off his tail and gave it to him last week.
Anyway, your horse was loved and lived to be old.
Find peace in your heart as you've done him right.
For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places.