The poem is a list of losses. Over and over, the speaker repeats "turn into" to show how good things slip into worse versions: full meals become no meals, straight A's become failing grades, a cheerful child becomes a sad teenager. The repetition feels like a slow slide downhill, where each line adds more weight to the one before it.
The speaker seems exhausted and worn down. The imagery gets darker as it goes, with minds as jails and hearts as war scenes, and the line about fighting just to live suggests a daily struggle with the speaker's own thoughts and feelings. Judging by the details, this may be about depression or something close to it, though the poem never names it.
The ending hits hardest. After all that change, the speaker admits that "nobody cares enough to notice." The mood is bleak and lonely, and the plain, almost flat tone makes the hurt feel real rather than dramatic.