This definition is straight from Wikipedia; "Impostor syndrome (also known as impostor phenomenon or fraud syndrome or the impostor experience) is a concept describing individuals who are marked by an inability to internalize their accomplishments and a persistent fear of being exposed as "fraud". Imposter Syndrome Definition
What does it mean to "not internalize" accomplishments? Basically, not being able to integrate achievements and assign value to yourself.
Feelings of self-doubt can plague all of us — and in some cases these harbored doubts threaten to derail our work lives. A place to begin an exploration of the origin of these negative thoughts is "Where do your doubts originate?" Typically, these are cognitive distortions and negative thought patterns. Much of the time, "Imposters" feel lucky for their success, not necessarily competent or confident. In fact, There is an ever present fear of being found out and exposed as a fraud. These feeling serve to drive anxiety, fear, and more doubt. Fear of failure, making a mistake or not knowing something makes this cycle of anxiety and sometimes depression worsen. If you would like to view a NYTimes article about Imposter Syndrome, click on this link. NYTImes Article.
Doubts and fears can arise due to the notion that if things come to easily, the tendency is to discount the value of the process which lowers self-esteem and increases the feeling of being an imposter. One last observation, confidence is the ability and recognition that you can "do something." Self-esteem is how you "value" what you do or the attribution to it. Getting an award, promotion, or achieving some goal is essentially discounted with thoughts like, "I don't deserve it", "I could have done better", "Someone else is better than me." Correcting the Imposter Syndrome means confronting your fears, negative self-talk and the way you value yourself. Work on validating and affirming yourself and accomplishments. Learn to accept compliments and make yourself an MVP of your own life.