I came across another link Seeyalater that you should read. It explains how the relationship goes and what a narcissist will actually "train" their partner to do. This is something I have been working on myself as I had been "trained" myself by my older sister who needed a narcissistic feed from me, I did not understand this however and even my husband as he does have narcissistic traits that were intertwined with his alcoholism and lack of maturity. It was always "my fault" and now that I have PTSD, I can get very triggered by reminders of having to give in somehow to keep the peace.
If you can understand this "now", you will hopefully allow yourself to see it developing so you do "walk away". It can do a lot of damage if dealing with it long term. They do not reach out for help either so that can be a red flag you need to pay attention to as well. They say, "I don't need help "you do" even.

Sometimes it can be hard to distinguish whether a person is one, or is the victim of one, so pay attention to the signs. You do "not" want to become a codependent.

Narcissistic Victim Syndrome: What The Heck Is That?