So often we move through our days half asleep, carried along by a stream of worry we mistake for our own life. The chains and the guards are still there, yet something wakes. Peter came to himself. That phrase holds the whole thing. Waking is not an escape into a better story but the return of the one who was always present beneath the fear, the awareness that had been covered over.
Once that stillness comes back, the mind quiets and seeing grows clear. Only then could he say he knew for certain he was free. A person who steps out of the noise of the anxious mind sees where they plainly stand, and finds themselves already delivered.