composed, collected, balanced, equanimous, self-possessed, self-contained, self-collected, dignified, assertive, distinguished, more...

ungraceful, clumsy, awkward, ungainly

poised for action, poised for success, poised for failure, poised for a fall, more...

calm and collected,   ready to pounce,   stand ready,   ready to spring,   good under pressure,   ready and set,   calm and confident,   ready and confident,   calm but energetic,   action ready