Answer:
I am a type of animal that hang out in the mist
I run smoother than any rhyme, I love to fall but cannot climb. What am I?
What is always in front of you but can't be seen?
I come with a train and go with a train and the train doesn't need me but can't go without me.
Teenage girls are pros at creating me. Learn me in classes.
No matter how little or how much you use me, you change me every month.