The phrase "take a wrong course" can refer to making a mistake or taking a misstep in life. To express this same idea in different words, you might say that someone has "gone astray," "taken a detour," "lost their way," or "veered off track." These synonyms all convey the sense of being headed in the wrong direction, whether it's in terms of a career path, a personal relationship, or some other area of life. Other possible synonyms for "take a wrong course" include "miss the mark," "go down the wrong road," "stray from the path," and "make an error in judgment".