It's never easy but you're doing the right thing. We recently had to put one down we'd had for about 16 yrs. He was just about deaf and had been blind for a couple of years, but managed to get around very well. He finally stopped eating and we knew it was time, he never suffered at all.
Give it a little time and you will still have all of the good memories and none of the bad. We still talk about him most every day and we know we gave him the best life we could. He was a rescue and ran this house for many years. Bless you and your pup