Sweet chestnut is the remedy for people who have reached the limits of endurance. They have explored all avenues and see no way out of their difficulties. They feel there is nothing left for them but annihilation and emptiness.
Whereas people in a Gorse state decide to give up when there are possible solutions untried, the person in a Sweet Chestnut state is genuinely at the end of the line: theirs is appalling, final despair.
In this extreme state, the remedy helps us remain masters of our lives, and renews our hope and strength. Sometimes a way ahead may open even when we expect it least.