“Liarse la manta a la cabeza”, a Spanish expression that means: acting without having reflected about the main situation. The translation is: “Tie a blanket over your head”
There are many theories about where the expression comes from, but one of them refers to Medieval battles, when the soldiers used blankets to protect their head from the rocks, arrows or the hot oil that the defenders threw to protect themselves.
Another theory is bound to Rodrigo Díaz de Vívar. It was probably minted to the Cuarte battle (1094). The city was attacked by Almoravides and couldn’t resist at all, so Rodrigo decided to make an ambush for the enemy, during a foggy night. He ordered his army to tie a blanket over their heads and attack without looking behind. Well, they won the battle even though lots of soldiers were off after it.
By the way, this Spanish expression should be used in a non-reflected situation that may have a risk. It is not necessary to be serious, it could be a scolding or a low exam mark, for example.