Since a lot of folks out there are wondering whether they're with what is called a Catalyst Soul Connection (look it up if you don't know what that is) or maybe even a Karmic Soul Connection although it's difficult to say a connection is entirely Karmic in nature, there's many out there who are dealing with relationships that may or may not really be "the one."
That being said, here's a helpful video that may assist you in looking at your connection in case you've ever wondered if you're dealing with a connection that you simply can't shake.
The general consensus is that when a narcissist gets their hooks into you, they can be hard to shake. The person I often refer to as my "False Twin" was very hard to shake, for example. I'm not saying he was narcissistic, just hard to shake.
I have also seen of late, many folks asking things like, "Am I talking to my "one" or am I dealing with some kind of a narcissist?"
Dr. Ramani here gives an excellent explanation which may help you differentiate for yourself.