Ok guys, It is now two weeks since my BPDex decided she was abandoning the relationship and moving out, and one week since she actually did move out and I went 'No Contact'. And what is more, I'm actually doing pretty well with it! Now, ok, I'm a cheating a little, as this is the second time I've been left by a BPDgf, so it will naturally have been easier this time around. But I think a lot of my recovery has been due to the fact that I didn't make the same mistakes as last time. So I wanted to share a few tips with you all on how best to handle a BPDex abandoning the relationship.
1) Grieve, but reflect.
It is natural, when the other person decides to leave, to be sad. I am a fully grown, emotionally stable man, and I don't mind saying I cried. But you must also look back at the bad times with your BPDex. The rages, sulks, arguments... . even, in some cases, violence. Was this the loving, supportive relationship you had been looking for? Of course not. Remember that... . you are escaping abuse, not losing love.
2) Understand. It was not you, it was them.
The type of BPD person who abandons relationships will have a long history of doing so before you. When they said that was just because they hadn't met someone as special as you, this was part of the 'seducer' phase. The reality is, whatever bad things they said about their exes were probably untrue, or at least exaggerated. Your ex will continue in this vein, continually failing in relationships, and abandoning them when they realise their anger issues are back, and when they blame their next partner for this as well.
3) Don't waste time begging them to come back.
If you do, you will quickly see how little you mean to them now, and that hurts. Better to understand it straight away, and not put yourself through being told how awful you were, how it was all your fault, and how they wish they'd never met you. In their mind, they are now the victim, and you are the abuser. This is how they self-justify how badly they will treat you.
4) Go 'No Contact' ('NC' as soon as possible.
The longer you try to talk to your ex, the more they will use this to hurt you. They will ignore messages, even if they previously promised they never would, because they 'know how much that hurts'. Why would they behave like this? Well, because they know how much it hurts. They will say the nastiest things, designed to attack your deepest insecurities. They will flaunt new partners in front of you. Do yourself a favour, and don't let them. They will soon get bored and leave you alone.
5) Get mutual friends to help with the No Contact.
More will understand than you think. You don't need to tell them why, just that it is necessary for you to have nothing to do with them. Ask them to not tell you about how the ex is doing, who they are seeing, etc. Ask them not to invite you both to the same events. Anyone who doesn't do this for you is not a real friend anyway.
6) Get out and socialise.
Find a friend to go clubbing with, join a club such as Drama, or find some other way to both reconnect with your old friends and meet new ones. Even if you don't feel much like it, make yourself do it, and concentrate on enjoying yourself. Life goes on, and you will be comfortable with this quicker if you encourage the process within yourself.
7) Sort out the 'mechanics'.
If you were co-habiting, or otherwise dependent on your ex for more than companionship, then you also need to put your affairs in order going forwards. Make sure you are financially stable. If not, take whatever steps are necessary to make this a reality. Once you are free of other worries, such as how you will pay the bills on your own, this will help you feel better about striking out on your own. If you need to downsize your property, or take on a tenant, do so.
8) Sort out any access through a third party.
If you have children, these can be used as a favourite weapon against you. Don't get drawn in. I feel like a bit of a fraud here, as the kids in my last relationship were hers, not mine, and they didn't live with us, so it is naturally easier for me. But if you want to continue a relationship with any children, or let your ex do so, then get a grandparent or someone else you can trust to make the arrangements and hand-over the kids. Otherwise you may find your ex still playing games with you over access.
9) Find someone who can let you offload.
In the US, of course, it sometimes seems to us Brits that therapists must outnumber the rest of the population; you all seem to have AT LEAST one!

But if therapy is not something easily accessible, such as here in the UK, then turn try and find a friend who can take a phone call or an email each night. Find two or three. They will need to be very good friends, but try a few out; you may be surprised by which ones are there when you need them most. You could also try mailing someone on here, and striking up a pen-pal conversation. Someone did just that with me, and I'm very glad, as our mutual outpourings of thoughts, feelings etc have been hugely helpful to me.
10) Adjust to the idea of being single
Look around at your friends. Are the single ones permanently depressed and miserable? Of course not; they are comfortable being independent. Sure, they might be looking for love; for the most part, we all are. But get your head around the idea that you are your own person now. You can do what you want, go where you want, when you want. You can talk to someone else without worrying about jealous rages. You can just sit and chill out, without being told off for some perceived slight. You will actually learn to enjoy this, and if you've gone 'NC' you will no longer be tempted to try and 'win' the break-up by being first to see someone else (because THAT'S NOT going to lead to a healthy relationship!). Once you are just being 'you', then anyone attracted to you will be so for the right reasons (hopefully!).
Well, folks, those are my thoughts. I hope they're useful to some of you. Please feel free to add any tips of your own, and also feel free to let me know if you want any further advice on any aspects of this. Stay strong, and good luck!