A person's rate of growth often depends on how clear their current life challenge is. Many people are not unintelligent or lazy, but because their goals keep shifting. What truly sets people apart is not how much they have learned, but whether they can consistently invest in a core goal. The biggest cost in life is not learning too little, but wasting limited time and energy on unrelated goals. True growth often begins with a single sentence: in this phase, I only do this one thing.