Narcissistic abuse is painful and healing from this kind of abuse is a long journey. One of the things that can help you to heal is to learn how to feel empowered. You need to build back the self confidence that was crushed down by the narcissist.
Many of us were abused during childhood in some way. Emotional abuse and mental abuse can be as damaging to the way the brain functions as any other kind of abuse.
Much of our brain wiring occurs before the age of six. There may be very early trauma that you do not even remember. If you have been the target of abusers then somehow you were programmed in a way that makes you susceptible to manipulative people.
When you were growing up you were supposed to be given certain brain software during the developmental stages. You should have been taught how to set boundaries to protect yourself. You should have been taught how to tell when someone is not treating you in the way that you deserve.
The ability to spot a liar and to tell when someone is lying to you can help you to feel empowered. It will make it harder for people to deceive you.
This lesson by David Snyder is very interesting. I recommend that you watch this. You will learn about why people accept lies, even when they realize that something is not quite right.
You will see how to tell signs of lying. The most important thing for you now is that you begin to focus on how you deserve to be treated. You should be in relationships with people that want to have genuine communication with you.