I'm so sorry to hear about Shaker, budboy. It's never easy to lose them, especially when they've been with you so long.
I've always looked at our time with our dogs as (to borrow a phrase) "Excellence on loan from God", and eventually, God calls in the loan. While the loan is active, though, you reap the benefits--love, companionship, joy, and, yes, even sorrow that touches your heart. But ask yourself if you'd give up a moment of it? Every second is a blessing and changes you for the better.
The end is always hard, but you do your best and give it over to God. So don't second guess yourself on the end game--concentrate on all the blessings Shaker shared with you throughout his long life.
He was a very lucky boy to have had you! 15 years!! Job well done, budboybudboy77.
Shaker