Fear and self doubt: I find myself questioning whether or not I'm smart enough or if I can make it. I have to take a few seconds and reset my mind. Everyone has felt that way at one point or another. It's part of the process. Pushing through fear, uncertainty, and doubt is necessary to be successful.
Listening to people who aren't in the game: Plenty of people will have advice on how to invest in RE and they've never even bought a primary residence. Don't compare yourself to others, but look at a few people who you consider successful and see if you're completing the same daily, weekly, monthly, and yearly actions to achieve that level of success. If you want to be the best basketball player in the world are you going to listen to Michael Jordan and Lebron or are you going to listen to that guy from high school who sat the bench?
People who struggle with imposter syndrome believe that they are undeserving of their achievements and the high esteem in which they are, in fact, generally held. They feel that they aren’t as competent or intelligent as others might think—and that soon enough, people will discover the truth about them. Those with imposter syndrome are often well accomplished; they may hold high office or have numerous academic degrees.