Two short lines carry a lot here. The speaker is looking at someone they care about and recognizing a breakdown they've been through themselves. "As I did" is the key phrase: this isn't sympathy from a distance, it's the sting of seeing your own past suffering repeated in another person.
What the speaker feels is mostly helplessness. They know what this "madness" is like from the inside, yet that knowledge doesn't give them an answer. If anything, it makes things worse, because they understand exactly how bad it is and still can't say how to pull the other person out.
The mood is quiet, raw, and a little desperate. There's no flourish and no resolution, and the poem simply stops on the admission "I don't know how." That bluntness makes it feel honest, like something said in a low voice to no one in particular. We don't learn who the other person is or what caused the collapse, so the poem stays focused on the speaker's fear and tenderness.