I am the....

I am the bullet that one uses to kill another,
The man who pulls the trigger puts me in the position to kill,
I'm innocent till i'm set loose to ruin another.
I am the tire that flattens on the road,
No one pays attention till they can no longer drive to their destination,
you fill me up then go on till I have no more air once again.
I am the water that one drinks,
they pick me up when they have thirst,
then forget I was even there.
I am the girl one has abused,
I loved them till I saw no use,
they say it's my fault but now they are the one with the lawsuit.