Earlier quoted context omitted.
Well, Aristotle said something very similar: It is the mark of an educated mind to be able to entertain a thought without accepting it.
This one is much better and on the mark. Fitzgerald's quote needs a corollary, which appeals to intelectual honesty. If reason definitively tells you x, but you want to believe y, then you might be tempted to abuse Fitzgerald's quote.
The ability to hold mutually contradictory ideas at the same time and continue to function is something we all do - it's a fundamental part of the human psyche. There's nothing special about it. It's just that we generally do it by compartmentalising the ideas to different parts of our lives.
Dealing with multiple contradictory ideas at the same time and knowing and accepting how they contradict, is very different.