Answer:
If you lose me you may cause people around you to lose me too.
I jump when I walk and sit when I stand.
I am in truth a yellow fork from tables in the sky by inadvertent fingers dropped the awful cutlery. Of mansions never quite disclosed and never quite concealed the apparatus of the dark to ignorance revealed.
Light me up in backyard gatherings
I am bought by the yard but worn by the foot. What am I?
Soldiers fight it but never changes.