Is it normal to suddenly lose all desire to interact with a twin flame after spending time together, and what can I do about it?

What drives a narcissist to treat relationships like a game of collecting people and possessions?
How can you protect yourself from being scammed by someone with narcissistic traits, especially if they're trying to deceive loved ones?
Is it weird to never reach out to a friend again after you get done spending time with them, even though you had a good time with him/her?