Answer:
I come with a train and go with a train and the train doesn't need me but can't go without me.
I am quick when Iām thin. I am slow when Iām fat. Wind is my worst nightmare.
I am round as an apple, deep as a cup. All the King's horses can't pull me up. What am I?
I start new then become old. Start clean but be one dirty. I usually start big then become little.
To cross the water, I'm the way. For water I'm above, I touch it not and truth to say, I neither swim nor move. What am I?
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?