Answer:
I'm sometimes white but most often I'm black. I take you there but never bring you back.
I begin your sentences.
What's 3/7 chicken, 2/3 cat, and 2/4 goat?
I can be swallowed But I can also swallow you.
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.
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.