na-adjective, noun
happy-go-lucky; carefree; easygoing
Describes an overly optimistic, carefree attitude, often with a nuance of irresponsibility or lack of seriousness. Can be used as a noun or adjectival noun.
See also: 雅楽
彼はいつも太平楽なことばかり言っている。
He's always saying carefree, irresponsible things.
そんな太平楽な考え方では、問題は解決しないよ。
With such a happy-go-lucky way of thinking, you won't solve the problem.