Too Much Too Soon

I am not on loan,
but I am a loan:

I am not in the boat,
but I am beside it,
some of the time beneath it,
and too often holding on for dear life:

I am not the plane's pilot,
but I am its wing walker
balancing myself as well as can be
in the wind and air,
the mist of cloud,
gatherings of birds:

I am not the mountain,
nor am I the mole hole
or even that slight indentation in the cave
everything already too dark:

I am not for sale,
but I can be.