Go the extra mile: to go beyond what is necessary or expected in order to please someone, achieve something, or get something done correctly. If you go the extra mile, you make a special effort to do or achieve something.
I was 20 and had just finished my first degree when I asked my fathers advice on how to approach the world of work. He had a long and distinguished career in the Indian Army and rose to become commander-in-thief of a million men. He was a soldiers soldier and his men adored him. His manner was strict and firm, but he was very friendly. He appreciated and trusted people and gave them freedom.
”Come and see me in my office if you want to talk to me about work,” he said. So I made an appointment with his ADC and went to see him. He had a huge office and I felt very small. ”You are starting out and you will be given a lot of tasks to fulfill” he said. ”The first thing is always to do something to the best of your ability. Then the second time you do it, give it that little bit extra.” What he was saying was: ”Take the initiative; be innovative; be creative. Always go the extra mile.”
If you say that someone is willing to go the extra mile, you mean that they are willing to make a special effort to do or achieve something.