The Biggest thing that makes you a perfect supply for a Narcissist
"Emotional vulnerability" makes you an ideal target for a narcissist, a psychopath or other types of abusers. Vulnerability, and the need for support, arises when your spirit is low, such as suffering bereavement or having left an abusive relationship.
The narcissist presents himself/herself as ideal support, doing and saying whatever gives the impression of care while taking advantage of your vulnerability. So, at such times, it's unadvisable to form new relationships and, thus, avoid becoming a source of narcissist supply.