Something good is worthy of fighting for. How could there be the happy ending after all the darkness and shadows? Without Sam, Frodo couldnot get far alone.
"It's like the great stories, Mr. Frodo, the ones that really mattered. Full of darkness and danger they were, and sometimes you didn't want to know the end because how could the end be happy? How could the world go back to the way it was when so much bad has happened? But in the end, it's only a passing thing this shadow, even darkness must pass. "