Object Inconstancy:

Object inconstancy is vacillating from idealizing someone to devaluing them when frustrated or disappointed, causing anxiety or insecurity in relationships. This can lead to anger and resentment, making it difficult to forgive and move on. Object inconstancy is a significant factor in understanding and treating borderline personality disorder (BPD) and narcissistic personality disorder (NPD). It enables people to:

• See people as all good or all bad, vacillating from idealizing someone when they are happy with them, but quickly devaluing them when they experience frustration or disappointment. 
• Struggle in relationships, becoming anxious or insecure, fearing abandonment or rejection. 
• Experience anger and resentment for extended periods, making it difficult to forgive and move on.