Frankly, I feel your pain, I truly do - I had my little 17yo Mini Foxy put down about 6 months ago and whilst I was devastated to lose him, I took so much solace from knowing that he'd had a fantastic life and now he was no longer feeling old with aches and pains but instead was frolicking with his mate of 15yrs, a Golden Retriever. When I managed to pull myself together and think along these lines, I was able to feel happy for him and privileged that it was me who gave him that life, my tears stopped and were replaced with a shaky smile.