affable, breezy, devil-may-care, easygoing, happy-go-lucky, laid-back, mellowcalm, collected, composed, cool, coolheaded, equal, level, limpid, peaceful, placid, possessed, recollected, sedate, self-composed, self-possessed, serene, smooth, together, tranquil, undisturbed, unperturbed, unruffled, unshaken, untroubled, unworriedeven, even-keeled, steady, well-adjusted, well-balancedimperturbable, nerveless, unflappable, unshakablecentered, disciplined, equable, self-contained, self-controlledcarefree, nonchalant, unconcernedassured, confident, self-assuredaloof, detached, dispassionate, indifferentrelieved, tranquilized(also tranquillized)