There comes that time when you have to decide to put your beloved pet to sleep. You've read about my experiences here and at my other blog. Francis W. Porretto has a heart-wrenching post about reaching that point with his dog, Bruno. My sympathies go out to him and my prayers go out to Bruno in heaven.
The pain will slowly pass and then (as I've done myself) you head down to the local animal shelter and take home a new bundle of love just waiting to give you new experiences and joy.