What Was I Thinking?

Braxton had been my Australian shepherd  for almost 12 years and I was thinking I best start thinking about a new puppy.  Get one before Braxton dies.
It  would be an easier transition for me and the puppy.  Not sure why I thought that.
I had become aware that Braxton was slowing down, not as able to jump into the back of the Jeep when we were going someplace so I thought his joints are getting stiff just like mine so I would help him up.  When he stopped jumping up on the bed at night I knew there was a problem rearing its angry head. He would pant continuesly and it didn't matter what time of day or the weather.  So out came my big book that answered or should have answered all of my questions concerning Aussies.  What I found I didn't like.  Heart worm.  Off to the vet to be checked but the vet said he couldn't find anything.  So I started giving him some stuff for joints.  The panting didn't stop.  He still ate good and would follow me almost everywhere.
With that going on I watched him more carefully.  Then he would just go outside and lay in the shade and pant.  How was I going to make the decision ?  When was I going to make that dreaded decision?
When I bought Braxton as a 9 week old puppy I had said I wouldn't do any Heroics in health care for him when he got old.  Now it was my time to really stick to my guns.  He was just a dog!!!