Just found this thread and want to give you hope from the other side. I separated 4 years ago and it is only in the last year that I have felt some peace. It is a long journey but you will get there. At times I felt it would never happen.
After years of emotional neglect, financial abuse, gaslighting, manipulating and his anger I ended the marriage. I had hoped it would be amicable but he said if I divorced him he would "unleash hell on me" and he did. Not because he loved me but because I was damaging his reputation.
We went to mediation and it was traumatising. It ended up in court. I became very ill, hospitalised for surgery and he still continued his relentless battle against me. The only benefit is that family & friends who had never seen that side of him finally "got" what I had been dealing with. He threw everything at me - court for finances and children access and a horrendous smear campaign. Everything was being done to try and disrupt my happiness.
At times I wasn't sure if I could cope but here is what helped.. find some support from those who can relate to disordered individuals. There is nothing worse than being patronised by well meaning people who don't have a clue what you are dealing with.
Dr Ramani has been mentioned already and totally agree. Binge watch her videos to help you remember it is them, not you and they will not change. Get legal advice from someone who knows high conflict individuals. I didn't and I ended up financially weaker. I have had to accept that and learn to make peace. I could go back to court but judge my health over money. There is an American lawyer on YouTube who has some useful tips with how to manage legal proceedings with a narcisstic. Some points might help.
Accept your sadness and the fact you may miss them. That is because you are "normal" and you commited and loved them. That will fade over time but it takes time. Don't have guilt for being suckered in by them. I spent time thinking why didn't I see it...but I am empathic and trusting and they are arch manipulators. I have had to learn to be less naive and trust my gut instinct.
If they are being nice they are either trying to hoover you, have an self serving motive or they are getting supply from somewhere else. Ex immediately started an affair with a friends wife which they kept hidden for a considerable time. I now see some of his demands where caused by him trying to shape his life with her.
Once their affair was out in the open he flaunted it to the dcs and myself. At times it hurt but I recall how he treated me at the outset. A few years down the line I can see how she is having to serve his agenda. They DO NOT change.
I am now no contact except for essential children contact on email/text. We have zero face to face interaction which means we alternate school events. Whilst this is a loss for me and children it helps me feel safe (he became menacing at meetups).
Get rest when you can, do yoga, mediation, go out for solitary walks (I found a place in a forest where I would go and sob and then resume my day). You may need ADs as ptsd is common after narcisstic abuse but generally not needed long term.
Please trust that you will get through this. I had many dark days and read threads of normal break ups with deep sadness as felt mine was never ending but there is light.
Good luck, you are not alone and others know what you are going through