"However, what gets us from experience to understanding is reflection. True, repetition and practice help us to learn but they do not substitute for the process of actively thinking about how we did, what we did well and what less well."
Improving learning through reflection – part one & two, Karen Hinett, The Higher Education Academy.  link 

"Awareness and reflection are not merely symptoms of developments in learners, they bring about the developments. It is through engaging students in reflecting upon the process and outcomes of their studying that progress is made."
 Teaching Students to Learn: A Student-Centred Approach, Gibbs, G. 1981, The Open University Press, Milton Keynes, p. 91.

"Reflection leads to understanding, which in turn leads to more informed action. Effective reflection leads to a better understanding of social problems and to the quest of better solutions". link