How can dating a narcissist change you?

Dating a person with narcissist traits can be quite draining.  The narcissistic personality is one of the mental health disorders that has become notoriously known as toxic.  The toxicity stems from a childhood where many unhealthy behaviors developed.  Given the depth of how these traits are developed and from such a young age, it is a bit easier to understand how their toxic traits can feel so strong.  So if you are to find yourself in a relationship with a narcissistic personality, then having a strong sense of boundaries will be very important.  However, if those boundaries are not well maintained, then here are a few ways in which you may notice changes within yourself:

1. Isolation: It is quite common for people with narcissistic traits to try and pull you away from your loved ones.  This is usually so that they can feel more in control over you.  Sometimes they will use charm to try and pull you away from others, talking to you about how they want you all to themselves.  Other times, they may try to convince you that everyone else is the “problem,” and you need to stay away from them.
2. Low self-esteem: Typically, at the beginning of a relationship with someone encompassing narcissistic personality traits, they will compliment non-stop.  However, you will quickly find that when they are upset with you or trying to control you, they will use language to berate you and bring you down.  You may start to feel bad about yourself, which is understandable given that this person is telling you how awful you are.  
3. Guilt: Someone with narcissistic traits, again, will focus on ways to feel in control.  Try to remember, from their point of view; it is what will help them feel safe.  And they will do anything to ensure their sense of safety.  Even try to put you in the position to be blamed for things when you are not at fault.  Narcissistic personalities very rarely take accountability for their own actions; they may say things like, “I wouldn’t have don’t that if you….”  Leaving you in the position to feel like no matter what, you are always in the wrong.

These behaviors listed above are not seen at the beginning of the relationship, but as you build closer to connection, they will use that connection to try and hurt if you.  Again, it is important to maintain very strong boundaries with this person to preserves your emotional health.