Contrary to popular stereotype, alcohol doesn’t increase your impulse to do stupid or destructive things; instead, it simply removes restraints. It lessens self-control in two ways: by lowering blood glucose and by reducing self-awareness. Therefore, it mainly affects behaviors marked by inner conflict, as when part of you wants to do something and part of you does not, like having sex with the wrong person, spending too much money, getting into a fight—or ordering another drink, and then another.
Do you want to learn more about willpower? Read the book.