Devil May Care /devəlmāˈker / adj. 

Definition: The term devil may care refers to someone who seems carefree and unconcerned about the consequences of their activities.

Etymology: This idiom first appeared in print between 1765 and 1795. By 1815, it appeared as an expression or oath.

In a Sentence

If you want to be successful, you must shed your devil-may-care mentality.

Ms. Wilson favors flashy lettering and painting epic-scaled maps, which are devil-may-care about geographic accuracy.

With her devil-may-care exuberance, the Iron Lady actress lost her shoe as she made her way on stage at Sunday night’s event in New York.

Synonyms 

Foolhardy, Reckless, Irresponsible

Antonyms 

Responsible, Uptight, Cautious