“You must say the words quickly, and not in a high voice. And if there is any fear in you, or any doubt, this will not happen. For you must learn that doubt is the destroyer of works of magic, and thus be careful of your processes and your fear.” - Idries Shah, The Secret Lore of Magic. (1957)
Doesn’t that just say it all? “Doubt is the destroyer of works of magic” - so the requirement is to find a place within the self strong enough to circumvent it. A place beyond doubt - perhaps not entirely without doubt, since that seems difficult to believe in, but a place where doubt has been met and answered and (at least temporarily) satisfied.
And I also like being careful of your fear - not negligent of it, in other words. Fear can be paralysing, but being careful of it seems to give it a place to exist without letting it run the show. Not to pretend these things - doubt and fear - don’t exist, but to acknowledge their potential crippling powers, seek to understand them and thus remove their influence to clear the path for magic. For magic is intrinsically change, and both doubt and fear inhibit and stonewall change.
Happy New Year!