Can we handle knowing our minds in depth?

I read recently that there are two reasons we humans don't walk around in a continuous state of fear: denial and distraction. The premise is that the world is indeed a dangerous place, and we need these mechanisms in order to function.

With mindfulness meditation, we bring awareness to these mechanisms, eventually seeing beyond them to the underlying realities of our situation.

I once read that Jung thought most people wouldn't be able to handle the results of Buddhist meditation practice, that it would disturb important mental structures and we'd become less able to function in the world. Jung was a smart guy. Why was he wrong? Or was he wrong?

A friend who's a meditation practitioner has a couple of friends who've reached "first path" or "stream entry", a stage of practice where a chunk of one's sense of self becomes significantly less solid. She said that her friends, while glad about their achievements, are a bit cranky at the loss of that more solid sense of self.

We are just animals, evolved to reproduce. There is no reproductive advantage to knowing one's own mind. Our minds are not built to know themselves. It seems a bit conceited of us to think that we can do this safely.