anonymous Feb 11th 2011 !⃝I think this song is about cutting.
The girl/woman suffers from depression, because something really bad must have happened in her life, something she cannot tell anybody (opens up for nobody) and "something [that] is scratching its way out, something [she wants] to forget about".
I assume that this something is rape, but it could also be something like a break-up or the dead of loving person de facto painful memories.
This painful memories bring her to the edge of suicide. So she cuts herself (narrow line), but "she can't decide" if she really wants to take the final step and so it just "never hurts/nearly works" for her.
Furthermore she keeps cutting herself, because she wants to drown the painful memories, that keep "scratching [their] way out" and forget them all.
This way it "nearly works" but they're coming back and as a result she's caught up in a cycle.
Obviously, she feels pretty alone with her problems and is afraid of others finding out about them (A part of you that'll never show/You're the only one that'll ever know).
It's some kind of normal, that people who cut themselves are ashamed of their behaviour and don't want the people around them to find out, or so think.
Additionally, the narrator thinks that cutting became a routine for her and tells her to think again about the reasons, how the whole thing started and find a way to deal differently with her problems.
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