And he could not tell why the struggle was worthwhile, why he had determined to use to the utmost himself and his heritage from the personalities he had passed.
He stretched out his arms to the crystalline, radiant sky.
"I know myself," he cried, "but that is all." (2.5.249-251)
By the end of This Side of Paradise, Amory Blaine has no clue why (or if) life is worth living. But it looks like he's going to go on living anyway, out of sheer habit.
All he really knows for sure is who he is and what he thinks. But there's a pretty big world out there that he doesn't understand at all, and at this point, it seems as though Amory is destined to feel out-of-place wherever he is. Then again, maybe knowing himself is the first step he needs to take before expanding out and finding a home for himself… somewhere.