I think there was one where a snake 'recovered' and stopped seizing but ended up being so disabled that it had to be euthanized anyway (I think there were 2 ribbons involved, and one died from the seizures and the other had to be put down). It's not like with dogs/cats where they can get the emotional benefits of spending more time with people; keeping them around when they're suffering is just frightening.
But seriously, you did the right thing. There's no 'getting better' from that.