"The only concrete help you ever get from me is that I attack your self-reflection. If it weren't for that, you would be wasting your time. This is the only real help you have gotten from me." ~The Power of Silence.
Ultimately this is the crux of what don Juan did. Through the books with Carlos. What it boils down to is ego and completely upsetting self-reflection.
This can be down on your own. but it is difficult without a teacher, like Carlos had. Without a teacher, group, or even dear friend who is skilled in the art. But it is definitely not impossible, esp. if the warrior is brutally honest. They can attack their own reflection but this really requires knowing the self and how you tick.
It requires a lot of work, shutting off the internal dialogue, and stalking of the self. But other people are invaluable in attacking self-reflection. Check how others respond to you, and what feedback they present. Other people are great mirrors of the self. We know ourselves through looking inward, but we also know ourselves by going outward and seeing ourselves in others. Those we love, and even those we despise. Once we do these things, we can see ourselves clearly, and eventually do away with it completely.