And the end doesn't really support this theme...or define it.
Had I ended the story at the point where the girl walked away, maybe it might have been, "No matter how many things you overcome, there will be something that beats you." (Notice the theme that isn't story specific and more "declarative statement" specific.)
Now, here's now this, stopped shorter, is different from what you had: it implies success on success on success...then failure. It reflects the actual story.
But, since I didn't cut the end short, even this theme doesn't quite capture the paragraph.
I look forward to more thoughts from others.