Before, now, later

Reliance

A scorched film is as useless to a photographer

As a jammed rifle to a soldier

But you have a new film

And a rifle cleaning kit for me

A blunt pencil is as useless to a writer

As a smashed lens to an astronomer

But you have a sharpener

And a new lens for me

Oxygen is as useless to a tree

As carbon dioxide to a human

But you take the oxygen out of me

And I drown in carbon dioxide