James challenges confident planning by saying life is "a mist" that appears for a little time and then vanishes (James 4:13–14). He says boasting is evil and that such confidence is arrogant (James 4:16).
In James 4:13–16, James addresses people who speak confidently about future travel, business, and profit. He challenges that confidence by pointing out how little anyone knows about tomorrow and how brief human life is. This paragraph sits in a larger stretch where James confronts patterns of speech and desire that create conflict and self-exaltation (4:1–12) and then moves to warnings about wealth and oppression (5:1–6).
James 4:13–16 critiques a certain kind of future-talk: detailed business planning spoken as if the outcomes are secured (“we will go… spend a year… trade… make a profit”). The text’s explicit reason is human limitation: people do not know what tomorrow will bring, and life is brief and fragile (“a vapor”). James is not attacking planning itself.
A careful answer keeps the immediate passage, the book's argument, and the whole-Bible storyline together, so the question is answered in context instead of as a detached idea.
Start with James 4:13-14, then read the surrounding section so the answer stays connected to the passage's flow.
13Come now, you who say, "Today or tomorrow let`s go into this city, and spend a year there, and trade, and get gain."
14Whereas you don`t know what your life will be like tomorrow. For what is your life? For you are a vapor, that appears for a little time, and then vanishes away.