Narcissistic personality disorder is not the same thing as being selfish or treating a partner badly.
UK mental-health guidance has changed over time in how personality disorder is described, and diagnosis belongs with qualified professionals. A person can behave selfishly, lie, manipulate or control without meeting criteria for any personality disorder.
The reverse matters too: reducing everybody with a personality-disorder diagnosis to 'abuser' is inaccurate and stigmatising. Abuse should be identified from abusive behaviour and patterns of power, not assumed from a diagnostic label.
Ask what happened rather than what category the person belongs in.
Did they repeatedly humiliate you, isolate you, control money, monitor your communication, threaten you, deny obvious events, punish boundaries or make you afraid of their reaction? Those behaviours can be discussed directly.
You do not need to win an argument about whether the person is a narcissist before deciding a pattern was harmful or abusive.
The search for a diagnosis can become another form of staying psychologically attached.
After a confusing breakup, reading about labels can initially make things feel coherent. But endless videos, quizzes and comment threads can keep your attention fixed on understanding the other person instead of rebuilding your own life.
Try setting a boundary around research. Learn enough to name behaviours and find support, then shift some of the energy toward your routines, friendships, values and future decisions.
If there was coercion or abuse, use the language and services built for that problem.
Domestic-abuse organisations focus on patterns such as control, intimidation, isolation, threats, financial abuse and psychological abuse because those are actionable regardless of personality diagnosis.
If you were frightened, controlled or unsafe, specialist support is more useful than trying to establish a remote psychiatric diagnosis of your ex.
Use boundaries that respond to behaviour, not labels.
You can decide not to accept insults, repeated uninvited contact, financial manipulation or pressure to disclose private information without first knowing why the person behaves that way.
A boundaries book can be useful during recovery if your difficulty is holding a limit without feeling guilty. It is not a diagnostic tool and should never replace specialist safety advice.
Your recovery does not require the final explanation to come from them.
Some relationships end without a satisfying admission, apology or explanation. Waiting for the other person to validate your interpretation can leave your recovery dependent on the same person whose behaviour confused you.
Build the explanation you need from observable facts, trusted support and what you want to protect in future relationships.