A two-headed jar, empty from inside

Feeling like an useless fool,

Whose only purpose is to BE,

Future that I cannot rule,

Past for me is a senseless sea.

Looking at the sands of time,

I am not sand, nor the time,

What am I?

A two-headed jar, empty from inside.

 

Feeling like an useless tool,

Whose only purpose is to BE.