The speaker describes what it is like to watch their own mind sink into despair, and to recognize it happening. The first time, they don't see how far gone they are until something pulls them back. After that, the struggle is out in the open. They recover and rediscover joy, but then everything slips "like sand through fingers," and this time they can see it coming.
The mood is raw and weary, with flashes of bitterness. Hopelessness and anger "take shifts," and the speaker feels betrayed by their own mind, asking "Why?" as though demanding an answer. Short, plain lines make the pain feel immediate and unpolished.
Yet the ending shifts. The speaker is tired but doesn't want to give up, and admits that having no reasons makes it harder, "but not impossible." The final lines suggest that even anger can let a little hope through, which leaves the poem quietly, stubbornly hopeful.