Tootles, the Lost Boy first encountered as an elderly man in Wendy's home, has literally lost his marbles. When Peter returns them to him by the end of the movie, they prove to be the cure to his confusion and malaise, and allow him to return to Neverland. Captain Hook, in contrast, is not so lucky: He's lost his mind, and there's no toy that can bring it back.
Captain Hook has, in the years since Peter's departure, fallen apart. He appears to be suicidal and even points a gun at his head. He craves attention and will go to great lengths to receive it. He wants, above all, to finally slay his sprightly foe. This, he believes, will fill the sucking void within his soul.
Now, Hook isn't doing all that badly, all things considered. His quarters are luxurious, and one might imagine he'd be happy without Peter around to mess up his plans. But the midlife crisis comes for us all, and he, like so many at that time of life, longs for the past. When Peter returns, he even lets him train, in the hopes of a real fight. Captain Hook wants to battle the Peter Pan because, quite frankly, that was when he was most challenged and happy in life. But as any adult can tell you, that's only a band-aid applied to a grievous wound. If only Neverland had therapists.
