Oprah Winfrey believes her beloved dog Gracie died for a reason.The TV mogul, whose two-year-old Golden Retriever died in May after choking on a plastic ball, has spoken of her "stabbing pain and disbelief" but is determined to learn from the tragedy.She revealed in O, The Oprah Magazine: "I don't believe in accidents. I know for sure that everything in life happens to help us live."Gracie did more living in two years than most dogs do in 12. This dog lived every moment as though it were her last. Her life was a gift to me. Her death, a greater one."The chat show host was lunching with friends on the fateful day, while Gracie was exercising with her dog walker and two other Golden Retrievers.Gracie found the clear ball - belonging to Winfrey's 12-year-old Cocker Spaniel Sophie - in the grass and swallowed it.Oprah recalls: "I ran barefoot out of the house and found the dog walker and one of my security guards pumping her chest."Just as I reached them, the security guard looked up and said, 'I'm sorry,ma'am. We tried everything. I'm sorry. She's gone.'"I stood there dazed, stunned, crying - and watched as they placed her in the back of a golf cart, her still-warm body with the lipstick stain from my kiss on her fur."The 53-year-old has never had children but currently has two Cocker Spaniels and two Golden Retrievers.