The first two decades of our lives were easy.
Learn to read, make friends, get good grades. Get through puberty, forget about puberty, get good grades.
Take the SATs, get into college, survive college, get good grades. The path was pretty clear.
The third decade of our lives is hard. Up until now we've followed a relatively straightforward mold. The minute we graduate, this mold disappears. There's no defined "next step"—instead we have options.