The adage: "Practice makes perfect."
however, experience teaches that only "perfect practice" makes perfect. In order to improve at a skill, mental or motor, requires reflective practice. In order to improve at a skill, the learner must assess performance and make adjustments as needed.
"Defining Reflective Practice." Scholarship of Teaching. University College Dublin. n.d. 20 Dec. 2012.
For three definitions of reflective practice.
Link: http://www.ucdoer.ie/index.php/Defining_Reflective_Practice