BPD is one of the many personality disorders that severely impacts a person’s ability to regulate their emotions leading to unhealthy patterns of thinking and behaving. It affects how they feel about themselves, and negatively impacts their relationships with others. The world is viewed in black and white, all good or all bad. Their views swing very rapidly- if things go according to them then you are their best friend, the minute they sense even a slight criticism they perceive you as their enemy.