Fear of abandonment.
People with BPD are often terrified of being abandoned or left alone. Even something as innocuous as a loved one arriving home late from work or going away for the weekend may trigger intense fear. This can prompt frantic efforts to keep the other person close. You may beg, cling, start fights, track your loved one’s movements, or even physically block the person from leaving. Unfortunately, this behavior tends to have the opposite effect—driving others away.Helpguide.org
Efforts to avoid real or imagined abandonment, such as rapidly initiating intimate (physical or emotional) relationships or cutting off communication with someone in anticipation of being abandoned.NIMH
An intense fear of abandonment, even going to extreme measures to avoid real or imagined separation or rejection.Mayo Clinic
Frantic efforts to avoid real or imagined abandonment by friends and family.NAMI
This is one of nine traits used to diagnose borderline personality disorder. Many are common to other disorders, and you should seek professional guidance (if accessible) if you are concerned about a diagnosis.