Pain

You... cannot see me,

But I am... in plain sight,
So many of you know me,
Though I'm not black nor white.
I have no colour,
no clothing do I wear,
But you will all get to meet me,
Whether you are dressed or you are bare,
Some I may visit,
but not for too long,
Some I will stay with, until you age on,
For some I will pass you,
I could visit a friend,
I could go away,
or I could stay till the end,
If you think you don't know me,
Then you best think again,
I am one no one likes,
I am one they call Pain