Answer:
To unravel me you need a simple key, no key that was made by locksmith's hand. But a key that only I will understand.
What do you throw out to use and take in when you're done?
What has a mouth but can't chew?
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.
What type of paper can you neither read nor write on?
Those with eyes bigger than their stomach will definitely leave the restaurant with one of them. It is named after a house pet as well.