"an assumed air of doing difficult things with an effortless mastery and an air of nonchalance" (Count Baldassare Castiglione in Book of the Courtier.)
"... a deliberate nonchalance, the illusion that even the most difficult things are easy... Anything unessential is disdained. The presentation is so direct that it seems to be improvised, and so natural that it seems it could not go any other way." (source)
Either you have it, or you don't. I think it is a gift, like one is blessed with a talent upon birth. It is used to advantage or squandered/wasted. &;-)