I've seen it a lot on Twitter lately. Authors, even some who have achieved some measure of success, are mentioning that they don't feel as if they've "made it", that they're not "real authors". These feelings are not alone. In fact, a great many authors, myself included, have Imposter Syndrome.
According to the Oxford Dictionary, Imposter Syndrome is the persistent inability to believe that one's own success is due to one's own efforts and abilities. In a world where people are looking for tricks or shortcuts, it makes sense that people don't believe they deserve to be where they are or do what they do.
A quick web search on "tips to overcome imposter syndrome" brings up dozens of results. It's a very common topic.
So what can you do if you feel as if you have Imposter Syndrome?
Accentuate The Positive Remind yourself of your achievements and what you have done. Have you received great reviews? Focus on them.
Acknowledge Your Feelings Perhaps there is a reason which makes you feel that way. Name it. Shine light on it, so you can change how you think about it.
Don't Stay Silent Talk to someone. Vocalize your feelings to others.
The usual advice is to "fake it until you make it", which isn't bad. It also can be difficult so try to surround yourself with some positive people who can help.