Ending a relationship is always hard, so I guess the simple answer is: the hard way. Ending a relationship with a pathological liar will be made harder still as s/he will use her tactics the same way s/he did during the relationship: to manipulate you into a state where you will serve their needs, not yours. I know I make it sound like a voluntary or intentional decision on their part but it may not be! Regardless, the effect on you will be the same. I think the best you can do is plan ahead, distance yourself as much as you can emotionally and expect the worst of behaviors. I found I can prepare for some of the worst things to happen in advance by writing them down and planning in detail how I can/will react. It helps me to remain calm and not get sucked into the vortex....