The speaker here is addressing someone who is hurting and pretending otherwise. It could be another person, but the blunt, repeated command, "Stop lying to yourself," reads just as easily as someone scolding themselves. The lie is simple: *I'm fine.* The poem refuses to let that stand, insisting "You're not alright."
The imagery is bleak. The tunnel has no light at its end, so there's no promise that things will improve on their own. Nights are worse, when the mind is quiet and has "no remorse," attacking without mercy. The line about the head "devouring itself" makes overthinking feel like something physical and self-destructive.
Still, the poem isn't only despair. It pushes toward action: "go get some help," "You must get out." The prison is one the person built, which suggests guilt has trapped them, but also that they might find a way out. The mood is urgent, raw, and tense, like a worried friend who won't stay quiet.