Shadow and Light Source Both

How does a part of the world leave the world?
How does wetness leave water?
Dont' try to put out fire by throwing on
more fire! Don't wash a wound with blood.
No matter how fast you run, your shadow
keeps up. Sometimes it's in front!
Only full overhead sun diminishes your shadow.
But that shadow has been serving you.
What hurts you, blesses you. Darkness is
your candle. Your boundaries are your quest.
I could explain this, but it will break the
glass cover on your heart, and there's no
fixing that.
You must have shadow and light source both.
Listen, and lay your head under the tree of awe.
When from that tree feathers and wings sprout on you,
be quieter than a dove. Don't even open your mouth for
even a coo.