Do narcissist always try to lower the self esteem of the girlfriend?

In a Word....yes! They cannot help it. It's part of being a narcissist. Once the idealization period is over in which they try to capture the girlfriend/partner by portraying the Mr Prince Charming act which makes you fall for them, then they go into the devaluation phase which sadly, and I know from recent experience, involves the belittling, demeaning and whittling away at the partners self esteem, self worth and very existence until they are left confused and wondering what they did wrong in the relationship. Why he was never pleased with anything. How he could go from thinking you were the best thing since 'sliced bread' to treating you as though he'd just trod in something! The thing is the partners do nothing wrong!! This usually starts once they know they have you by seeing a commitment or by declaring your love for them or once they feel your attention is faltering or they no longer sense your uncritical admiration. This phase can last as long as he sees fit for it to last. There is no time scale. The next phase is the discarding phase. This comes about either through boredom or his pursuit of adoration, attention, admiration elsewhere. He will merely discard a partner and has no empathy or remorse about doing it either. Why should he? He is incapable of feeling human adult emotions. Love is a thing that will evade him all his life. He will go from one woman to the next in the pursuit of love but will never, ever find it. To him a girlfriend/partner is a mere object and you don't have remorse or empathy about throwing out an old kettle when it no longer works!! This is the narcissists world. Sadly and unfortunately for his 'victims' we realise all too late. They are unable to feel intimacy or love. They can only feel superior or inferior and rage and hate....and most of all FEAR. They are unable to have a loving, close intimate relationship with anyone, they may aspire to it but it will never be achieveable, even their own children, as most adults do. Depending on which type of N he is, be it cerebral or somatic, brain or body orientated, they both have one thing in common and that is to CONTROL. Their mission is have total control over their partner, their life and everything in it even her past! Their fear is of not being in control. Apparently it is something that stems from childhood. But I'm unable to comment on that as my guy never spoke of his childhood. All I knew was that he had a domineering father, who commited suicide when my guy was 24yrs old and not when he was a child. That was just guesswork from little snippets that he disclosed when he was off-guard. If you're still with the guy, you can try to leave of your own accord, as I tried several times, only for him to harrass me and stalk me until I gave in and took him back. I had to wait for HIM to decide that I was to be discarded for him to leave me alone. Then you get to pick up the pieces of your life, try to repair the damage that he's caused to your self esteem, to your family and friends and try your best to carry on whilst he's already moved onto someone else. Good luck.