[Eowyn:Lady of Rohan]

Let's see. If Sam had kept the ring, he would have thrown it into the fire of Mt. Doom. He already knew that it was the purpose to go with Frodo. If one failed the other would take over and destroy it. The temptation to keep the ring wasn't strong with Sam. He knew what would happen in the long run. Sam isn't the type to fail. He would have gone and cast the ring into the fire.