Answer:
As I went over London Bridge I met my sister Jenny; I broke her neck and drank her blood and left her standing empty.
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.
My second is performed by my first. A thief by the marks of my whole might be caught. What am I?
Travel a mile and I will change, travel a million and I will end as I started. What am I?
I will go within you and destroy you. Only because you wanted me too
Runs over fields and woods all day. Under the bed at night sits not alone, With long tongue hanging out, Resting at your feet until we go for a walk