Composed

calm cool relaxed easy collected tranquil serene levelheaded unflappable imperturbable self-possessed poised sedate temperate unruffled at ease confident easygoing sensible possessed clearheaded assured together untroubled staid dispassionate soothed quieted nonchalant commonsensical disimpassioned repressed suppressed angered cool as a cucumber not turn a hair have one's act together sure of oneself keeping a stiff upper lip keeping one's shirt on