go mad
1. To become insane or mentally unstable. All this noise in the house, day in, day out—I feel like I'm going mad! She went mad at the sight of her child lying lifeless on the cot.
2. To do something excessive or without hesitation or restraint. I decided to go mad and buy both the dresses I liked. A: "Do you mind if I eat your leftover pizza?" B: "Sure, go mad."
3. To reach an extreme or excessive level or degree. The president's new cabinet is made up entirely of her old friends and former classmates—it's cronyism gone mad!