It is so hard - I know you wish he could live on and on. It's especially hard when we are older because often our pets are such a huge part of our lives.
My mom who is 85 pretty much (on a day to day basis) only has her little dog. I know if he goes before she does, it will be so hard on her.
These things are never easy, no matter the age. Please know that you can come here to talk anytime - someone is always here and everyone is so nice and caring on this board