Testo: Mouthpiece. Can't Kill What's Inside. With This Regret.

I've locked my only exit, I've done this myself.
I want to go back, start it over again,
But I'll just waste my time with this regret.
Nothing I can do, just try to move on,
If only my conscience would let me, but there's no chance of that,
So I beat on myself, break everything inside.
Scratch at the walls, make my nails, empty myself...
Then I rebuild