When my little dog died several years ago (I'd had her for 12 years- the oldest dog I'd ever had), it made me feel better in the long run remembering that she'd been one seriously happy dog- taken care of, played with, well fed, and so on. 12-14 years is a pretty long life for a dog, so I figured that would be like me living to 85, and spending every day of it being fed for free, playing almost non stop, and getting my back rubbed day in and out
That dog had one nice life while she was here!
I know that probably doesn't help any right now and nothing to be said really could, but it's a nice thing to think about once that initial shock/grief goes away, which it eventually will. Hope you feel better soon