Probably one of the Devil's greatest lies is the image of hope as something fleeting and ephemeral. It ties into the lie that you have to effortlessly feel something for that feeling to be real. Just because I don't feel like there's gravity, or just because I can't see the movement of the floor as the world whirls endlessly through space, doesn't mean that those things aren't there, and the same can be said for things like hope.
Hope isn't just some flighty butterfly, something fragile and wispy. Hope is the woman praying daily at her husband's side in the hospital, waiting for him to wake and wondering if he'll remember her after his head injury.
Hope is the sailor clinging to the helm in the teeth of a gale, riding it out because he hopes and knows that the storm cannot last forever.
Hope is Samwise storming the tower of Cirith Ungol, not knowing whether he can truly overcome the orcs in the tower, but hoping that he can help his Master Frodo in some way at least.
Hope is the last stand of Húrin the Steadfast: holding the gap against the forces of Morgoth in Nirnaeth Arnoediad, the Battle of Unnumbered Tears, swinging his axe as he and his kinsmen fight to the death to protect the retreat of Turgon and the elves of Gondolin, shouting with each swing, "Aurë entuluva! Day shall come again!"
Hope is not something fleeting, something ephemeral. It can become such, because like any other emotion or feeling, it needs cultivation. But if you cling to it, if you hold it tight, then it will grow. If you let it, hope is a fighter, a shieldwarden, a warrior. Hope is not simple platitudes, but a knowledge that whatever things might feel like, the truth of the matter is different—no matter how hopeless things seem, things will not stay that way.