Here's an unpleasant epiphany:
The toughest of all arts/sciences/skills/talents? Is communication.
You may know all the languages in the world, even idiomatically, and all the nuances of tone, expression and words in all of them. You may know all the gestures and actions in the world that you can use to make yourself understood fully. Your body language may be perfection itself. You could, in potentia, have the power to convince even dust that it's God.
But communication will forever, forever be the toughest task to because it is entirely dependent on the dust paying heed to you.
Communication? Will forever depend on your audience.