Guys please help me understand the following passage?

"He knew the answer, but even that was not a full explanation. Different segments of the organism called John Kelly knew different parts of the whole story, but somehow they'd never all come together, leaving the separate fragments of what had once been a tough, smart, decisive man to blunder about in confusion and despair? There was a happy thought. He remembered what he'd once been, he remembered all the things that he'd survived, amazed that he'd done so. And perhaps the worst torment of all was that he didn't understand what had gone wrong. Sure, he knew what had 'happened' but those things had all been on the outside, and somehow his understanding had gotten lost, leaving him alive and confused and without purpose. He was an autopilot. He knew that but not where fate was taking him." Context: John Kelly is an ex Navy Seal, nam veteran who'd been through hell. This is where he picks up a totally random girl who happens to be on the interstate, but she hadn't been asking for a ride. Kelly was on his way home. Kelly sees her just standing at the side of the road and he pulls over so she reaches up to him and asks where he was going and he says he was going home and asks if she'd like to come along, she agrees. But he hadn't really given it a conscious thought before picking her up, it was totally random and now he's been wondering as to why on earth he is taking her with him, and why she'd agreed.. His wife and her unborn baby had died 6 months ago from a car crash.