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 make you weak at the worst of all times. I keep you safe I keep you fine. I make your hands sweat and your heart grow cold. I visit the weak but seldom the bold.
I give light by night, but not by day. I am wicked but not evil in any way. Wax for the most but always wane; except when I'm out, I stay the same. What am I?
I have a brother. However much we run we do not reach each other.
I can be simple or I can be complex. I can be found in this riddle or in everyday life. I can be shapes or even colors.
I flow from the Homerβs mouth when he sees doughnuts.