Answer:
Used left or right, I get to travel over cobblestone or gravel. Used up, I vie for sweet success, used down, I cause men great duress.
I can be cracked, I can be made. I can be told, I can be played.
I am round as a bowl, deep as a tub, but all the world's water couldn't fill me up.
I'm sometimes white and always wrong. I can break a heart and hurt the strong. I can build love or tear it down. I can make a smile or bring a frown.
They made me a mouth, but didn't give me breath. Water gives me life, but the sun brings me death.
What never gets any wetter no matter how hard it rains?