happy-go-lucky

carefree, casual, lackadaisical, nonchalant, unaffected, unconcerned, unfussy, unperturbed, untroubled, unworried

familiar, homey (also homy), informal

flexible, lax, lenient, permissive, pliable, pliant, soft

accessible, approachable

imperturbable, nerveless, unflappable, unshakable

amicable, companionable, comradely, cordial, genial, hail-fellow-well-met, hearty, neighborly, warm, warmhearted

blasé (also blase), breezy, cavalier, nonchalant

casual, easygoing, informal, laid-back, low-pressure, relaxed, unfussy