Carefree
Part of speech: adjective
Definition: Without cares; free of concern or worries; easy; casual; without difficulty.
Example sentence: In my solitude, many miles from men and houses, I am in a childishly happy and carefree state of mind, which you are incapable of understanding unless someone explains it to you.
Devil-may-care
Part of speech: adjective
Definition: carefree or recklessly irresponsible