Answer:
I am quick when Iām thin. I am slow when Iām fat. Wind is my worst nightmare.
What gets sharper the more you use it?
I tremble at each breath of air, and yet can heaviest burdens bear. What am I?
I take off my clothes when you put on your clothes. I put on my clothes when you take off your clothes. What am I?
I work when I play and play when I work. What am I?
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?