Its a hard thing to do. Sometimes i think he is all there and is happy but most times I think his body is still there but his mind is going. This morning he crapped while sleeping which has been normal for a while. He was up drinking water when I got up. I went to take him outside and he just stood there. Wouldn't follow my lead, if I let the leash loose he would take a few steps but that was it. He hasn't been able to walk down our three steps in a long time. I pretty much have to carry him outside.
I would have to say that he most likely is not enjoying life.