Riddle

This week we had to write a riddle using metaphor 

Guess my riddle

 

In the desert you will see me but never find me,
I was here before you and I will be here after you are gone.
You need me but won't like me if I surround you.
You will die if you have too much of me... or too little.
 I am free but am stuck on this planet.
You do not eat me.
What am I?