A very popular theory brought up when talking about learning a new skill is the ten thousand hour rule. It states that for someone to reach mastery of a skill, they must put approximately ten thousand hours of practice into that skill. Some have come out and modified this theory to say that ten thousand hours is to reach proficiency, but to master a skill one must put approximately 20 thousand hours of practice into the skill. These numbers are more of a guideline than they are facts. For someone to become very good at a skill, they must practice a lot. Everyone is different, and everyone learns at different speeds.
What constitutes practice is debated. It seems that the definition of practice is uncertain in this theory. Some musicians advocate that listening to music counts as practice, while other musicians deny this statement. Some will argue that visualization is practice, while others will argue against it.
What are your thoughts on the ten thousand hour rule?