blithe -
carefree and happy and lighthearted; "was loved for her blithe spirit"; "a merry blithesome nature"; "her lighthearted nature"; "trilling songs with a lightsome heart"
cheerful being full of or promoting cheer; having or showing good spirits; "her cheerful nature"; "a cheerful greeting"; "a cheerful room"; "as cheerful as anyone confined to a hospital bed could be"
blithe -
lacking or showing a lack of due concern; "spoke with blithe ignorance of the true situation"