Putting in a lot of time might make you tired, but simply working a lot (even if it’s 10,000 hours over the course of your career) isn’t enough to make you a top performer. It’s not the same thing as practicing deliberately. Most people who think they are working hard are merely developing the skill of being in the gym, not the skill of making baskets or scoring points in exam.
Case of problem solver…..
Consider the activity of two students practicing a technical subject questions for 2 hours. Student A solves 16 exercise problems , Student B does 8. The student B solves 2 questions and then day dreams leisurely and takes several breaks to talk to check Facebook updates and never bothers going to professor. Student A visits professor regularly to discuss some inside tricks and techniques .furthermore, he keeps the record of questions he did. If Student A gets the wrong answer he notes down where he made the mistake, whether it be in misinterpreting the question , calculation or concept mistake. The student A reviews his mistakes after solving couple of questions. To characterize their two hours of practice as equal would hardly be accurate. Assuming this is typical of their practice routine and they are equally skilled at the start, which would you predict would be the better problem solver after only 100 hours of practice?
Each student in the example above could boast about practicing for two hours, but only one of them is practicing deliberately.