Answer:
I am free for the taking. Through all of your life, though given but once at birth. I am less than nothing in weight, but will fell the strongest of you if held.
A tiny bead, like fragile glass, strung along a cord of grass.
I'm not really more than holes tied to more holes. I'm strong as good steel, though not as stiff as a pole.
Thousands lay up gold within this house. But no man made it. Spears past counting guard this house, but no man wards it.
I bind it and it walks. I loose it and it stops.
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?