失之千里，差若毫厘

Explanation: Subtle mistakes that can lead to large errors. 　　Source: "Astronomical Notes on the Sui Dynasty," a mile, if the least bit of difference, a well-behaved elephant, can experience what the rest! " Thesaurus:  a miss is as good as a mile, A slight mistake will result in a great error in the end A slight mistake will result in a great error in the end