Congruency... You appear better than you are. If a guy puts expensive business clothes on, polished shoes, watches and tie on and start working for a law firm, most people will expect that he is a successful lawyer. However, the second he opens his mouth everybody realizes that he has no clue about law. That's usually the moment when sort of disappointment comes, people were expecting more than they got because he appears like an attorney, but he is not... So they ask, why is he faking his appearance? Why is he pretending to be someone else when he is not...? They expected too much from him based on his appearance, yet he can't deliver any of that expectation...
Some people are very good at reading body language, they can read very quickly through personalities...
Similarly, you don't want to overshoot your appearance with girls. If you project strong and dominant body language while you are really not that dominant guy, there is sort of disappointment. She realizes that you are not who you are pretending to be. Some girls are VERY FAST in reading body language and recognizing congruence. They usually give you one quick window pretty much right at the beginning of your interaction, and if you don't start moving forward right away there they know you are faking, or they at least DOWNGRADE you to less dominant guy in their mind (which is still sort of disappointment)... They know you are projecting too much of a great lover, yet can't deliver even perhaps half...
You want to BE that guy, you don't want to pretend to be... A better way is downgrade your appearance and dominance first, just enough to level than she notices you... Then you show dominance with your actions (rather than appearance), this way she didn't expect much from interaction with you at first, but because of your dominant actions she now has to UPGRADE you to more of a lover in her mind, as you actually do things that only confident men can do...