Composed

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