Circe is referring here to the monster Skylla, but you can really apply her words to all forms of suffering. Pain, she tells Odysseus, is unavoidable.
(Eurylochos, in Odysseus's tale:) '"You are a hard man, Odysseus. Your force is greater, your limbs never wear out. You must be made all of iron, when you will not let your companions, worn with hard work and wanting sleep, set foot on this land, where if we did, on the seagirt island we could once more make ready a greedy dinner; but you force us to blunder along just as we are through the running night, driven from the island over the misty face of the water."' (12.279-285)