Reflective practice has been defined as

“The process of internally examining and exploring an issue of concern,
triggered by an experience,
which creates and clarifies meaning in terms of self,
and which results in a changed conceptual perspective.”
Practically speaking, learning from an experience can be enhanced by thinking in depth about what happened and what it means.  You should expect to consider how it has altered your opinion on how the world works and what consequences this might have for future decisions.  By predicting possible future outcomes of interactions you can be better prepared to respond in a more effective and efficient manner.
Reflection is a skill that many of us use informally and unconsciously on a day-to-day basis.  When undertaken as part of a structured and conscious strategy, the reflective process can result in more impactful learning.
 Thinking about how an exam went badly and feeling stressed about it is a common example of
informal unconscious reflection.
Sitting down after an exam to make notes about why you felt unprepared and how you could prepare better if you were to sit it again, is an example of
structured conscious reflection.

To reflect in a structured conscious way requires time and effort and may feel like a chore. However, with practice, the time and effort will reduce and the rewards of your efforts will increase. To adopt this skill will allow you to become a more effective and efficient learner which may help place you ahead of your peers. The sooner you learn to master this skill, the better.

Kolbs reflective cycle (1984)

Gibbs reflective cycle (1988)

Only a fool learns from his own mistakes. The wise man learns from the mistakes of others..”
Otto Von Bismarck
Once you have got to grips with the art of reflecting based upon your own experiences, attention can be turned to reflecting from the experiences of others.  Your own experiences are called primary events, whereas experiences of others are called secondary events.  Secondary events can include information that is written or spoken by others, such as reading books or attending lectures.
Interaction in groups of individuals is especially powerful.  We refer to this as a Community of Practice.  
Our online forum where we share learning reflections is an example of this.