What you don't see are the years of preparation that brought this athlete into form.
Great interviews arise, likewise, from careful groundwork.
This is the state from which great tennis players or basketball players or Olympic skaters operate. You'll need to quiet the negative self chatter in your head through meditation or visualization prior to sitting down in the meeting. Act spontaneous, but be well prepared. Be your authentic self, professional yet real. Engage in true conversation with your interviewer, resting on the preparation you did prior to coming to the meeting.