Today I posted several threads about the final discard from a very old friend who I suspect, I think accurately, of being a covert narcissist.

A few years ago I got into a romantic relationship with an abusive narcissistic. To help me go No Contact, and to recover, I took an online course. One thing that was taught is that to be healthy means to not have any "hooks" the narcissist can hang onto. The person who gave the course thought it was important to give up addictive behaviors. So I did that. I gave up smoking cigarettes...which was insanely difficult as I was pretty addicted. Then I gave up drinking because after quitting smoking my drinking started to increase. I became a vegetarian and even became a runner for one short year! Although marijuana is legal where I live and I happen to like marijuana...I gave it up.

I think these things do help to keep one protected from narcissists. That's not to say all narcissists have substance abuse problems. But they will use whatever weaknesses you have.