“Only fear and the unknown prohibit one from following their dreams.”

The alchemist, p. 141.
Variant: There is only one thing that makes a dream impossible to achieve: the fear of failure.
Source: The Alchemist (1988)

Chelsea FC, Doctorate Honoris Causa degree award (23 March 2009)

Introduction
The Female Eunuch (1970)
Context: The fear of freedom is strong in us. We call it chaos or anarchy, and the words are threatening. We live in a true chaos of contradicting authorities, an age of conformism without community, of proximity without communication. We could only fear chaos if we imagined that it was unknown to us, but in fact we know it very well. It is unlikely that the techniques of liberation spontaneously adopted by women will be in such fierce conflict as exists between warring self-interests and conflicting dogmas, for they will not seek to eliminate all systems but their own. However diverse they may be, they need not be utterly irreconcilable, because they will not be conquistatorial.

Google It: Total Information Awareness, 2016

The Photographer’s Wife
Gigi (1945)

"Supernatural Horror in Literature" (1927)
Non-Fiction
Variant: The oldest and strongest emotion of mankind is fear, and the oldest and strongest kind of fear is fear of the unknown
Source: The Complete Fiction of H.P. Lovecraft

Part Four, Chapter 12.
Blue Highways (1982)
Context: What is it in man that for a long while lies unknown and unseen only one day to emerge and push him into a new land of the eye, a new region of the mind, a place he has never dreamed of? Maybe it's like the force in spores lying quietly under asphalt until the day they push a soft, bulbous mushroom head right through the pavement. There's nothing you can do to stop it.

McKenna interview (1992)
Context: There's always fear of the unknown where there's mystery. It's possible to achieve a state where you realize the truth of life and fear disappears, and a lot of people have reached that state, but next to none of them are on Earth. There's probably a few.

Jocasta (Line 977?).
Oedipus Rex
Variant: Nay, what should mortal fear, for whom the decrees of fortune are supreme and who hath clear foresight of nothing? 'Tis best to live at random, as one may.