How we cite our quotes: (Chapter.Paragraph)
Quote #4
Thomas exchanged glances with Newt, who returned a look that had a little fear in it but was mostly full of curiosity. (16.35)
Curiosity is often related to fear: many things we fear are unknown, which is why we fear them. But if we don't know exactly what this fear is, of course we're going to be a little curious as to what it is.
Quote #5
He wanted his memory block finally cracked for good... But that desire was tempered by fear of what he might find out about himself. (23.9)
Another reason why Thomas is so mentally torn is that he fears how he played a part in the Maze construction. Not knowing your past is one thing, but being afraid of what happened in the past is another thing.
Quote #6
He thought he'd gotten used to the fear of having the disease, but with this Crank standing right in front of him, he was more scared than ever. (26.10)
"It's easier said than done" is a pretty good phrase to illustrate this moment. It's a lot easier to get over the fear of having a disease when you don't know what it looks like, but when it's staring you in the face, that'll resurrect some demons.