You do know those who "wing it" do come with years of hidden preparations, right...? It's what makes the "magic" feel magical. Shhh, the magicians would kill me for spilling their beans...

Ok, I'll throw you a lifeline. It's a battle between the imposter syndrome (I'm not good enough) vs. the Dunning-Kruger Effect (the person with the least ability thinking he/she can wing it). Two sides of an argument, two forms of justification.