What Am I, To You?

I am what I am.
I am everything you say and everything you think.
I am everything you hear.
I exist in many forms and can be found everywhere.
I can be fast or I can be slow.
I can be gentle or I can be angry.
I am few.
I am many.
I am with you always, from the moment you wake up.
I am with you even when you dream.
I am there from birth until death, and still beyond.
I am very old, and yet I am young.
I am recreated every day.
I cannot be forgotten.
I cannot be undone.
I am sometimes seen as petty.
Though often I am seen as strong.
I am beautiful, though not always treated as such.
I am often under-appreciated.
I am not easy to describe, but you cannot describe anything without my help.
You cannot think without me, and yet you probably rarely think about me.
Without sounding arrogant, you need me.
Every day you rely on me.
I am what sets you apart, from every other creature on earth.
I am all around you.
I am here.
And I am there.
I simply am.
What would you be without me?
You cannot even answer the question, for to answer would be to need me.
I am everywhere, and yet nowhere.
I am everything, and yet nothing.
I am, or I may not be.
And yet, I always am.
What am I, to you?