I believe it was Kant – at least according to my French philosophy teacher at school – who stated roughly that growing up means overcoming one's fears.
And perhaps the best way to overcome one's fears is to confront them head on.
This is called exposure therapy in modern psychology.
Maturity seems to me to involve both a process of ditching one's illusions, i.e. errors (as argued in my blog post Growing Up as Dis-illusion-ment), as well as vanquishing one's fears with regards to the world and others.