Difficult decisions.

The past few weeks I really have been lost in relativity when it comes to my 12 year old dog, Lucky. He has some sort of neurological disease and doesn't walk well, lost his hearing and some eyesight, and doesn't act the same. I just never realized what a difficult decision this would be. How do I know it's time? What if we are choosing wrong? But if we keep him alive, is he happy? Are we keeping him alive just for us? Back and forth, back and forth, we think we made our decision, then he will act perky for a little while, and we change our minds. Then he seems "out of it" and we are back on. Right now he is begging for people food- do you put a dog down who is still interested in food? Where is the line? Sometimes I think we have crossed it and at other times, I vaccilate. One decision I have made is that I cannot be there when he does get put down. I may regret it, but just can't do it emotionally. Decisions tend to not come easy to my husband or myself, and this decision is one of the most difficult for us to make. Let's hope we see our way through it...