Impostor syndrome (also known as impostor phenomenon, impostorism, fraud syndrome or the impostor experience) is a psychological pattern in which an individual doubts their accomplishments and has a persistent internalized fear of being exposed as a "fraud" (Wikipedia).
Symptoms: Anxiety, perfectionism, self-doubt, fear of failure
Comparing yourself to others
This may be one of the biggest reason you have ever felt like an imposter. Social media platforms are usually the place to fuel impostor syndrome symptoms since most of the things on these platforms are pictured as perfect, shiny and people are always happy.
You don’t see the downsides or the struggles that people go through and you feel even worse if you are having a bad day. Just be aware that the vast majority of people have similar symptoms and you are not alone.
Albert Einstein, Maya Angelou, Michelle Obama and many others all publicly expressed that they had often experienced feeling like a fraud in their career.
The solution would be to lower the consumption of social media, look back and be appreciative of what you have achived. You can always be grateful for the things you have done so far and the people you work with.
Being overly perfectionist may also impact the feeling of being a fraud when not accepting anything other than a perfect version and you are then left with the feelings of self-doubt.
Being precise is not the same as being a perfectionist. You may get external validation and praise, but you still feel like an impostor.
This can be seen in the tech sector, as well, where everything is moving at such a rapid pace. Knowing when a product or a feature is good enough is a really valuable trait.
Those symptoms may also be connected to your childhood if you have experienced feelings of not being appreciated enough. There are professionals you can talk to; they are there to help you.
Slowly and steadily working on accepting the work you do and the fact that many of your colleagues are in a similar situation can help you remedy it.
Impostor syndrome never truly goes away, but you can do a few things to remedy the effect it has on you:
Talk about it. You’ll see that you are not alone. You'll be relieved and feel freer because you shared your secret.
Look how far you've come. Remember past achievements and embrace positive feedback you got.
Re-frame ideas when in doubt, e.g. "If I can do this, I will be able to help others in the future and work with people as motivated as I am.".
Tell others when you appreciate their work. It can help them to cope with impostor syndrome.
Don’t be so hard on yourself. :)