Adjectives

(s)blithelacking or showing a lack of due concern“spoke with blithe ignorance of the true situation”
(s)blithe, blithesome, lighthearted, lightsome, light-heartedcarefree and happy and lighthearted“was loved for her blithe spirit”, “a merry blithesome nature”, “her lighthearted nature”, “trilling songs with a lightsome heart”