You should strive to be your best, of course. There's just so much to learn from other people.
I recently did a highly unscientific trawl across Harvard Business blogs. It felt like visiting a drop-in therapy center. Mindfulness. Meditation. Lead with your heart. Fears that block your creativity. Authenticity.
Holy smoke, I thought: it's all me, me, me. What about everyone else?
Don't get me wrong: I'm all in favor of being the best you can be. I just think there's a lot to be learned from other people, instead of investing all your love and attention on yourself. I have had the great privilege of interviewing a bizarre range of high achievers, from athletes to chefs, from musicians to scientists. I learn so much from asking the questions, and listening to the answers. These people rarely ask me about myself; that's fine because I'm doing my job and they're doing theirs.
Meditation, mindfulness, silence are all important and healthy. But so too is looking outside yourself--at the problems and possibilities that other people, cultures, and approaches have to offer. Leadership is at least as much about noticing other people--their needs, talents, and aspirations--as about interrogating and improving yourself. A healthy, humble curiosity puts you in a stronger position to understand and engage with the world. Personal development is a part of leadership, but it's only one part. If it doesn't connect you with the outside world, well, let's just say there's a ruder word for it.
I can't help but notice that even the articles on narcissistic leadership seem to be about how to minimize your own narcissism--and that the reason you would wish to do this is because otherwise your own career will be jeopardized.
I prefer a more expansive, externally-focused mindset: watch and listen to other people, languages, frameworks, structure, and everyone gets smarter. Leadership is about you--it just isn't all about you.