"Believe in yourself!" Err, how about I believe in the external world instead?
E.g there's lots of TV with the moral that you shouldn't be insecure. It's all about how you feel. Except, if you just go have a check, it doesn't matter how you feel about yourself, because you know what's actually going on.
Of course, narcissists can't do this. The outside world is too scary. Have to assume they already know everything, and it's merely a matter of weighing priorities correctly, because they damn sure can't learn anything new.
We need to be reminded, because we're all surrounded by narcissists. Apt to forget going and looking is even possible, since it happens so rarely. Reminder: you can just go look. Just try it and see what happens.
Maybe have confidence that you can win all competitions with narcissists, because you go and see what's there while they're lost in their own little world. Have confidence because you did what Gnon told you to and got the result Gnon promised, instead of doing what the bigger, nastier ego told you to do.