When I'm missing you may panic,
you always expect me to be there in need.
You can use me to build cars, trains, castles or spaceships,
the limit is only your imagination.
But if you travel to my origin, don't expect to see me.
Only you will find a lot of other helping means.
I smell like a flower, the sea or fresh air
but I dare you smell me right before I leave the world.
I'm slowly ripped to death, piece by piece
and yet my body is not covered by blood.
Children use me to play the walking dead,
my worst nemesis are cats.
I will provide a hint every time all lines are explained without getting the correct word; each line can be explained separately (title included).