Everyone is good at something. Everyone has something that they excel at over everything else. When one discovers that talent, they enjoy it because they are good at it. Since they enjoy doing it, they do it more and practice it often. Practice makes one better which further increases enjoyment. In other words, we enjoy that which we are good, we practice what we enjoy, and we get better at what were good at.
Deliberate practice, however is what separates the good from the great. If one truly wants to excel at that which they are good at, one must practice the fun stuff AND the not-so-fun stuff. It requires hard work, focus, and discipline.
In his book, Talent Is Overrated, Geoff Colvin defines what deliberate practice is and is not. He writes that deliberate practice is specifically designed, repeatable, highly demanding, and it isn't much fun. He also acknowledges that it is much easier to design practice for professions such as golf or music, but it is much more difficult in business leaders. He helps to identify practice models that business leaders can apply to raise level of performance from good to great.
Most people quit when the practice doesn't increase competence to a level that feeds back into enjoyment. This is where goal-setting and perseverance sets the excellent apart from the mediocre.