on the threshold

Sam: This is it.
Frodo: This is what?
Sam: If I take one more step, it'll be the farthest away from home I've ever been.
Frodo: Come on, Sam. Remember what Bilbo used to say: "It's a dangerous business, Frodo, going out your door. You step onto the road, and if you don't keep your feet, there's no knowing where you might be swept off to.