"You don't mind if I love him too, do you? I won't come between you." I respected her for asking, but I knew that she would come between us, so I found her preemptive denial to be disingenuous. (4.4-5)
This is the first time we see Enzo grappling with the fact that his life is going to change—and the fact that he has no way of controlling how other people's decisions impact him. It's also the beginning of a clear, albeit brief, turf war between Eve and Enzo. (Don't tell, but our money was on the dog.)
"Will you promise to always protect her?" [Eve] asked. She wasn't asking me. She was asking Denny, and I was merely Denny's surrogate. Still, I felt the obligation. I understood that, as a dog, I could never be as interactive with humanity as I truly desired. Yet, I realized at that moment, I could be something else. I could comfort Eve when Denny was away. I could protect Eve's baby. (6.20-1)
This moment between Eve and Enzo is about two things. First, Eve might be suggesting that she won't always be around to protect her daughter, so she's asking Enzo, and by proxy, Denny, to do it for her. Second, Enzo steps up to the plate here, realizing that while he can't take control of being human, he can take control of his own life, in whatever small way he can, and do what Eve asks of him.
From the moment they arrived, the Twins had been admonishing Eve for having her baby at home. They told her she was endangering her baby's welfare and that in these modern times, it was irresponsible to have a baby anywhere but in the most prestigious of all hospitals with the most expensive of all doctors. (6.26)
Here Eve's parents, in a dynamic feat of time travelling, try to control a situation that has already transpired. They fail because they can't time travel, but they certainly want Eve to know how they would have done things differently and how her decision, which ended up working out in the end, anyway, was completely wrong.
Dennis (Denny) Swift
"[Zoë] came early. You can't know what's going to happen before it happens."
"Yes I can," Denny said, "If I am any good, I can." (6.34-5)
If you think this is a little Yoda-trippy, that's because it is. Denny is trying to apply the rules by which he lives his racing career to his life, which is all very well and good when it makes him a prepared, focused person, but not good when he beats himself up for missing his daughter's birth or feels responsible for his wife's death. There are some things we can't control, Denny. Like whether they'll ever make a live-action reboot of The Lion King.
Maxwell and Trish
"My daughter, with a mechanic—no, with a customer service technician. Where did we go wrong?"
"She's always made her own choices," Trish said.
"But at least her choices made sense. She majored in art history…She ends up with him?" (15.21-3)
Aside from showing how judgmental Tweedle Dee and Tweedle Jerk Face are, this also indicates how much they want to push their own perspective of what is "good" for their daughter onto her. Maybe they just need to butt out, eat some demon peppers, and leave Eve alone.
Your car goes where your eyes go. (17.1)
This is the most repeated quote in the book, next to "That which you manifest is before you"—and they basically mean the same thing. You are in control of where you go, even if you don't know it, and you take yourself toward what you set out for yourself. Maybe it's not the most optimistic way to look at the world—but in some cases it may be. If you see yourself into a bad situation, you can see yourself out of it.
"Get me through tonight," she said. "That's all I need. Protect me. Don't let it happen tonight. Enzo, please. You're the only one who can help." (23.109)
This is another instance when Eve relinquishes control of her own life to someone else, once again Enzo. She asks him to watch over her because she's too afraid to fall asleep and succumb to the terror that's lurking for her in the night. Fortunately, Enzo makes an excellent guard dog, just not against demon zebras.
"Sometimes bad things happen," [Zoë] said to herself. "Sometimes things change. And we have to change too." (27.9)
This seems like a pretty deep to be coming out of the mouth of a five-year-old, and like Enzo, we suspect that someone told Zoë this to help her grapple with the terrible news of her mother's illness and its aftermath.
Denny looked at me and held his hands out in front of himself. They were shaking. Denny didn't say anything, but he looked at his hands trembling and then he looked at me and I knew what he was thinking. He was thinking that if he just had a steering wheel to hold onto, his hands wouldn't shake. If he had a steering wheel to hold onto, everything would be alright. (31.80)
We think a steering wheel is Denny's solution to a security blanket, mostly because it represents a sense of control over his direction and destination. Who could blame the guy for wanting a little bit of control in a situation like this?
Dennis (Denny) Swift
"No one could force Eve to do anything Eve didn't want to do," Denny said. "I certainly couldn't." (29.104)
This interaction that Denny has with Maxwell and Trish after Eve's death shows that Eve has always been in charge of making her own decisions, especially those decisions related to her health. We see her time and again realizing that something's wrong with her but refusing to seek help. This decision was a way for her to take control of her life, even if that decision leads to her death.