take the ball before the bound
To anticipate something and, in many cases, act hastily or recklessly as a result. The phrase originated in reference to cricket. A: "I did try to tackle him! I just figured he would go left, but he went right." B: "Well, now we're losing because you took the ball before the bound!" I didn't study much since I thought I knew the material, but I must have taken the ball before the bound because that test was impossible.