1. Act with the calm forethought of a beheaded chicken —Herman Wouk

   In his novel, Inside, Outside, Wouk used the comparison to describe the behavior of political characters.

2. Careless as a child at play —William Winter
3. Careless as saints who live by faith alone —George Garrett
4. [Charles de Gaulle] has been abysmally careless, like a man running a bus over mountains, who forgot to equip it with good brakes —Janet Flanner
5. Ignore caution like a gambler with a hot tip —Anon

asleep at the switch Off one’s guard; negligent; having slow reflexes. This expression derives from early American railroad terminology. To switch a train is to transfer it from one track to another, and an unaware or negligent worker who was “asleep at the switch” could cause a serious accident. The expression is no longer restricted to railroad usage and can apply to any irresponsible lack of attention which could have adverse consequences.

give short shrift To pay little attention or give insufficient time or consideration to a person or matter; to treat in a cursory or perfunctory manner. Shrift is an archaic word for confession or absolution (from the verb shrive). Short shrift originally referred to the brief period prior to an execution during which a prisoner could make a confession to a priest.

The phrase eventually came into more general use referring to any brief respite or short period of time. Thus “to give short shrift” means to treat summarily or brusquely, giving little of one’s time or energy.

a lick and a promise A hasty and perfunctory way of doing something; a half-hearted or nominal compliance with a request or command. In this expression, lick is used in the colloquial sense of ‘a slight and hasty wash,’ implying a lackadaisical or superficial performance of a task. Promise implies an assurance that a more complete and thorough job will be done at some unspecified time in the future.

slap:bang Hastily, often without consideration of possible consequences; hurriedly; haphazardly. This expression was originally used to describe sleazy eateries and “greasy spoons” where one received fast service by “slapping” his money down to pay for food that was indelicately “banged” onto the table.

Thus, by extension, slap-bang came to refer to anything done in a quick, careless, and unceremonious manner.

slapdash Carelessly; in a hasty though thoughtless manner; hurriedly; haphazardly. Originally, slapdash was a technique of painting a wall to give it the appearance of wallpaper by “slapping” on a coat of paint and then “dashing” or splashing on spots or blotches of a contrasting color. Although slapdash is frequently applied as a criticism to a writer’s or an artist’s style, it is also applied in other contexts to denote careless haste.