Half way line

There's this line
sometimes invisible
not marked in chalk or ink
not like a sprint track
nor like a basketball court
just an imaginary line
that you just cannot cross-
it's the way it is,
the way it has always been
you may not have ever been told why-
but generally you don't have to be
you just know
and so-
you stand at it's edge
you can't help it-
you tempt fate,
just a little
dangle your foot in the air-
wonder how far you can extend it,
before you know you've gone too far
but, eventually you put it right back down
again
and stare
and wonder why-
you can't cross a line
you can't even see-
but know
is there
even when it's not