The speaker looks back on a job that put him close to death again and again. He opens with a striking contrast: he has never watched someone take a last breath, yet he has faced death in huge numbers, as the mention of toe tags suggests. Each one wore away a little of his humanity, until his feelings seemed to drop into an empty well, with no pain or grief left in it. He says that numbness reached even happy or hopeful feelings, not just sad ones.
The second half turns to the present. He lives with PTSD, which he calls a lifelong curse, and medication dulls it only partly. Watching videos that make him cry is his own way of letting the pressure out. The ending is loyal and painful at once: he still feels for his fallen comrades and would do the job again, even though it left him in what he calls Hell. The mood is heavy and plain-spoken, with a quiet pride running through the hurt.