What is it with expressions that pertain to self injury? "About to tear my hair out," "pulling my skin off," "banging my head against a wall," et cetera. Even common mannerisms like smacking oneself in the forehead when somebody else does something stupid. We also reference suicide -- "If she wears that to school I'll die!" "If I get a bad grade on this test I'm going to shoot myself in the freakin' head" and so on.

Why do you think?