Answer:
What is it something that you always have but you always leave behind?
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.
It has no top or bottom, but it can hold flesh, bones, and blood all at the same time.
What dress does everyone have, but no one wears?
What can you share and still have all for yourself?
People take me on walks and I run and have fun. What am I?