I had a terrible work ethic when I was younger, both in school and on the tennis court. See the problem was that I was a talented (somewhat) tennis player and got away with a lot of things however, I was never able to reach my full potential. 

There is a famous quote that goes something like this "Hard work beats talent when talent does not work hard"... 

Work ethic is one of the few controllable aspects of managing a career or just simply moving forwards. It is absolutely in your own hands on how hard you decide to work and how much effort you decide to put into your daily life. Whether that is work, relationship, sports or anything else. 

I believe that the "magic formula" starts and ends with work ethic as this is the most controllable pillar of all - maybe behind attitude... but that is for a different day. 

I have some regrets from earlier in my tennis career which I am not planning to repeat in my professional career. If you are also ambitious, I would advise you to give this work ethic thing a shot as it can be magical.