I wrote MANY poems along these lines during 9th and 10th grade when I was deep in the depths of teen angst. This is the only one that actually turned out any good.

Something is following me
something I can't see
No one knows it's there
it only seems to bother me

It whispers in my mind
trying to tell me something all the time
But I don't understand what the words mean
or why they always rhyme

Others don't notice when it's there
Can't they feel it in the air?
They step on it's shadow
They walk right by it and aren't aware

In the mirror I see its pale eyes
staring at me
It knows something of which I'm not wise
It knows what I am

It tries to tell me what it knows
but I don't understand
It tries to tell them what it knows
but they can't even hear

I call it The Nothing
and sometimes I wonder if it exists at all
or if I made it up cause I wanted something
to be there when I call

It told me something last night
which gave me a bit of a fright
It told me in a dream
things aren't always as they seem

It said, "The Nothing could be something
and the nothing should be true
The Nothing's only nothing
because The Nothing's you"