The phrase "roller coaster ride" is an idiomatic expression that refers to a situation or experience characterized by unpredictable and intense emotional highs and lows, ups and downs. It suggests that someone's life or circumstances are going through a period of great uncertainty, fluctuation, and change - often with moments of excitement, fear, joy, sadness, hope, and anxiety all happening in quick succession. The phrase is derived from the actual amusement park ride where passengers experience sudden drops, sharp turns, and other unexpected twists and turns that create a thrilling but unpredictable journey.