Put some distance between you. Disengaging is hard. Whether you were together for a long time or the relationship was very intense, your dreams, values, and emotions are tied to the other person - that's normal. If you were have some codependent or narcissistic traits , or are insecure - then you are even more entwined. This is why it is hard to let go.
The longer you stay connected, the longer it will take to disengage, heal, and move forward.
Initially, it is best to end all personal discussions - stay away from comments like how do you feel, what are you doing or making any value statements like you really should see a therapist.
Conduct your business and move along. Do not meet alone, bring an outside observer, or meet in a very public place. Keep the conversations strictly on the topic (e.g., exchanging the children, making a business decision, etc) and if the former partner gets personal, end the conversation. The same advice goes for e-mail, if it gets personal, don't respond. Send personal mail back unopened (e.g., cards, etc) with no note. Do not do anything that could be interpreted as a message.
All this will help you disconnect.
Your BPD partner may beg to return at the time of leaving or afterwards.
This is common. It can be confusing and painful.
Be prepared for it. Discourage it at the start by not engaging in the conversation - no matter how curious you are or how validating you may think it would be.
Encountering the "smear" campaign
An abandoned BPD partner may try retaliating.
This can be avoided or mediated somewhat by paying careful attention to the "Prepare for your Departure" section. If your BPD partner degraded previous partners, you should assume that they will "bad-mouth" you. Anticipate how you may be smeared and 'nip it in the bud'. Speed is important. Some smears can get ugly.
Put yourself above blame, be an adult, don't get defensive - get on with your life.
Disturbed dreams, ruminations, doubt
A healthy person processes events through their dreaming, so your dreams may continue to be about the situation or the BP for some time. These dreams may go away, only to crop up later. Know that this is normal; use dreams as useful tools to analyze your reaction to the stressful events that triggered them. You may even gauge your progress by how quickly the bad dreams are fading.
You may also ruminate about your partner - go over it all day long, day after day. There are ways to manage ruminations - use them.
Feelings of doubt. Did you do the right thing? How is the person with Borderline Personality Disorder doing? Am I BPD too? Remember that you may have acquired such BPD traits as projection by merely being in contact with the disorder; a therapist will help you straighten out any feelings of doubt about these issues. Remember - your partner functioned without you before you met them -- as did you -- so relearn how to concentrate on your own needs and priorities again.
You may find yourself feeling isolated in your new surroundings and without a support group. You may feel that you do not have the energy left to make new friends, or even to reconnect with old ones. You may not want to go anywhere; you may also feel depressed. So treat yourself: go for a walk. Go to a coffee shop and be open to conversation. If you have hobbies, like painting, writing, reading, etc., use this new-found time -- when you are no longer dealing constantly with BPD issues - to pursue your interests. Go back to school. Look upon this as a new beginning. You will also find during this period that having your familiar things around you helps.
An Important Part of Healing is Mourning, Self-Examination, and Acceptance
Mourn the relationship.
The end of a relationship is a death of sorts and it is important to grieve. You will likely go through the stages of grief characterized by Dr. Kübler-Ross - Denial, Anger, Bargaining, Depression, Acceptance. These don't happen overnight, so be kind to yourself and give yourself time.
Focus on settling in to your new life, making new friends, telling family members and others about your transition, etc. - and most importantly, start setting new goals.
You may experiences a period of anxiety and tension from the experience, and it may be overwhelming. You may feel exhausted, with drawn, unmotivated, confused. You may experience depression or other stresses (e.g., PTSD). Be aware that these feelings will slowly subside; seek therapy as needed.
"Why" did you get into the relationship in the first place? This is a good time to examine your family background and see what blinded you to the fact that the BP was trouble (it is true that people with BPD are sometimes very good at hiding their illness, but in retrospect you will see that some early signs were there). You may have doubts or fears about making new friends or dating because you are afraid that you will once again choose a BPD partner. Keep in mind that you are now an expert on recognizing BPD symptoms, and so practice looking for these signs and deciding if your fears are real or not.
Continue therapy. Self-awareness is actually one of the "gifts" received from having been in an abusive situation; with enough work, you may actually come out of the experience as a stronger person. Be warned again, however, about rushing into any new relationships before you have fully processed the previous bad one.
While it is easy to be mad at either the person with BPD or the illness itself, personal recovery is greatly facilitated by acceptance and understanding on your part.
Borderline Personality Disorder is a real illness, not just a bad attitude and/or stubbornness. Find out as much as you can about BPD - this will help you to better understand what transpired - and what was (and was not) contributed by you.
This will also improve your ability to recognize unhealthy symptoms in other people and increase your social confidence and safety.
Give yourself time to heal