To Be Asleep At The Switch
Camarón que se duerme, se lo lleva la corriente
You sleep at the switch when you fail doing your job properly or when you don’t react quickly when an action has to be taken. As a consequence of that, your job will not be done properly or a big damage might be caused.
A switch at a railroad track lets one train to move from one track to another. Nowadays, this action is done by using a remote control from inside the train that will do the switch under the supervision of a control center. But during railroad first years, this action was done manually by an operator who was placed right at the switch waiting for the right train to be switched to pull a lever so as to move the heavy vehicle from one track to another. Not doing this accurately meant that two trains might run on the same track, sometimes on opposite ways and later on would possible collide.