leap off the deep end

1. To become crazy, frenzied, or irrational. A: "Now your father thinks the neighbors are plotting against him." B: "Wow, he really leaped off the deep end, huh?" Whoa, man, stop yelling! I only put a tiny scratch on your car—no need to leap off the deep end.

2. slang To begin doing something very complex, overwhelming, or unfamiliar, especially suddenly and without guidance, assistance, or preparation. I'm a little nervous about starting my graduate degree program, but I'm determined to leap off the deep end and give it a go. Those who go the furthest in life are the ones willing to leap off the deep end when a great opportunity arises.