Listen... I don't have a partner at the moment and I am not sure when I will again but if you have sex with your partner here is some advice I am gonna take that is very silly. One of the issues that come up with BPD is relationship object permanence -- we don't got it. When someone is out of sight, we forget all the good times and become convinced we are gonna be abandoned. It sucks. Here's a transitional object no one can take away from you -- get your partner to give you hickeys. On your tummy or chest or arms or wherever that isn't super visible. Easy to remind yourself of that time you were loved when you are splitting.