Answer:
What you do to determine the length of something
The more you take, the more you leave behind. What are they?
They're big and yet so far away, We see them at the end of day. They're small and they're above. We see them when we close our eyes, Each time we are in love.
The more you take away, the bigger it gets.
I am not alive, though I never die, to no one I've ever told a lie, today I can be god's warrior, and serve him with no horror, but tomorrow I might be devil's knight, for I am what ends the light.
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.