have one's wits about one, to

Also, keep one's wits about one. Remain alert or calm, especially in a crisis. For example, After the collision I had my wits about me and got his name and license number, or Being followed was terrifying, but Kate kept her wits about her and got home safely. [Early 1600s]

Manage by clever expedience rather than hard work or wealth. For example, Alan's never held a steady job but manages to live by his wits. This expression uses wits in the sense of "keen mental faculties." [c. 1600]

To be wide awake and alert. Wits in the plural has long meant keen mental faculties. Ben Jonson so used it in The Alchemist (1612): “They live by their wits.” About the same time, the expression of having one’s wits about one—in effect, ready to serve one—came into use. It appeared in James Mabbe’s 1622 translation of Guzman de Alfarache (“I had my wits about me”) and has been used ever since. To live by one’s wits, on the other hand, also implies managing by means of clever expediency rather than honest work.