There is nothing childish about it. It's dead serious, and failure to do so costs lives. And regarding that second part: Don't use words too big for the subject

There is nothing childish about it. It's dead serious, and failure to do so costs lives. And regarding that second part: Don't use words too big for the subject. Don't say infinitely when you mean very; otherwise you'll have no word left when you want to talk about something really infinite. -― C.S. Lewis