When there is no place safe and no safe place to put my head, when you feel the world shake from the words that are said...~Train, Calling All Angels
When Jim's older brother Sam left, Jim pretty much lost whatever faith he had had in the world to begin with—and it wasn't much. Because despite what Sam had said, he did understand that you couldn't be a Kirk in their house. He understood, implicitly, that Frank hated his father, and that Winona hated any mention or reminder of his father, and so between the two of them Sam—who acted a lot like his father—and Jim—who looked a lot like his father—could never really be who they were.
So the day Sam left was pretty much the day Jim lost his hope.
At first he tried to fight it. He tried to be a perfect kid, figuring if he was good enough they'd let him be himself, but that didn't work. In fact, it failed quite spectacularly. And that was when he decided to drive his dad's car off a cliff.
Now, granted, when he got older he'd tell every kid he ever met to never do something like that, because it would make every psychologist you ever met question your sanity before they even got to know you, but the truth was if he had to go back and do it again, he'd do the exact same thing. Because honestly, when he was cutting off Frank's message and laughing his ass off at the cop trying to pull him over and barely managing to throw himself out of the car before he went over the cliff with it, it wasn't only the first time he ever really felt like a Kirk. It was also the first time he ever really felt safe.