Answer:
Why is it so easy to weigh fish?
Send poorly behaved children to me and let them sit here.
I am one small little piece of paper yet sometimes hold lots of value. I am all you need to get in to big events but will cost you. I am an important part of travel. And if lost you're not coming.
I am easy to waste and unstoppable
Born in the ocean and white as snow. When I fall back to water I disappear without a trace.
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?