Green’s Dictionary of Slang

laissez-faire, nonchalant, carefree.

1967		P. Thomas Down These Mean Streets (1970) 30: I felt a fuck-it-all attitude.
1974		(con. 1945) E. Thompson Tattoo (1977) 362: At the gangway Jack snapped a fuck-it-all salute toward the fantail and went ashore.
1994		G. Indiana Rent Boy 108: Then, with a certain fuck-it-all bravado, she lifts the glass to her mouth and swallows it all down.