This split mind comprises two parts. One of the parts you are conscious of and you think is your entire self. You've identified with it.
The other part you are mostly unconscious of, having shut it out and pushed it out of awareness. You think that part is not yourself. You do not recognize it as you. And you project it onto/as 'others' to disown it.
The illusion is maintained so long as you are convinced that these two parts are separate, different, unrelated, and not one self. That means you fall for the illusion, the appearance, and the stories each has, that seems to suggest they're not `one`.
The best way to create that illusion is to set them against each other in a war of conflict, which makes them seem like enemies, or opposed to each other, as though they have absolutely nothing in common. This is a deception.
When you do not realize the two selves are part of one self, you are inside the illusion. You've bought into it. And you've identified with one part as your 'self'.
Awakening happens when you look more closely at the illusions which make it seem like these two selves are in fact separate.
Those illusions include any idea of victimhood or victimization, any idea of denial or blame or scapegoating, any irresponsibility or disowning of responsibility, any way in which you reject or judge or abandon yourself, etc. All forms of separation and attack. All of these attack ideas must be questioned.
What then happens is you realize that the 'other' that you thought was not you, IS a part of you. Anything you are experiencing IS chosen by you. And therefore, since you are the 'other' as well as the 'self', you have been doing all of these attacks to yourself. This is the key to salvation/awakening.
You have to get to where you can see that you are playing both sides of the experience. You are both the victim and the victimizer. You are both the attacker and the attacked. You are both the person running away and the person chasing.
And then you will see that both of these 'identities' both have a story. One of them (persona) has a sob-story about how it's just trying to be good and how the other (shadow) keeps attacking it. And the shadow has a story about how it's got nothing to do with the persona and wants to destroy its fake image. You need to look at both stories and realize, both stories are an illusion. The entire purpose of the notion that these two identities are 'separate' is to convince you that your Self - your identity - does not encompass both of them.
You are both of the parts of the split mind. Both of the false identities are within you. And this is where you have an aha moment of awakening. If both of these selves are within you, and if you are literally doing stuff to your 'self' ie you are making the shadow self do stuff to the persona self and vice versa, then you will realize that it is an ILLUSION that they are two separate identities. They are not separate selves. They are part of your ONE self.
Once your sense of self encompasses and is responsible for both of them, the illusion and story of each will be blown. You will see through it and recognize it is a deception. They're not really separate enemies after all, they're both you! And that means you see the sameness and oneness and unity of your identity. Your one self, rather than your dualistic selves. And overlooking (forgiving) these illusions of separation leads you directly to seeing your singularity, your wholeness. The oneness - singleness - of your identity. This is where you awaken.
You awake to a sense of self which encompasses all of the parts that you used to think were separate selves. And you therefore transcend all of those separate selves. You transcend the persona and the shadow. You see through the illusion that you were 'only' one small part of the contents of your mind - the illusion that you were the construct of a separate portion of mind (e.g. intellect). Seeing the oneness of the two becoming one, unifies you and reveals to you the true self.
You are whole, you are inclusive, you are unified, you are one self, you are not a split mind, you are not multiple personalities, you are not at war with your own self, you are not attacking yourself, you are singular, you are 'individual' not multiplicative, you are innocent and holy. Holiness means whole. Simply, awareness of this - experiencing it, is awakening. Letting go of separate selves and returning to one self.