"What can change the nature of a man?" -The Nameless One, Planescape: Torment
"Who are you?" -Sebastian, Babylon 5
We have, as humans, a dizzying and near painful amount of identifiers that we can latch on to. Some teachings on Kundalini Yoga (the ones I choose to trust anyway) say that is what Kundalini Shakti is, She is the power of self identification. Which is also why She is called the "World Bewilderer".
She is the great Power of manifestation, because what else is manifestation, but limitation to a seemingly fixed identity? A rock is a rock until it is worn to soil. Soil is soil till its nutrients are used up, and it turns to sand. Sand is sand till it is turned to glass, or eaten by some birds to grind food in their gizzards. And on, and on.
As human beings we are in a fairly novel position to change the force of our identity. As magicians we have the even more novel position of being able to make it more than "simply psychosomatic". As a person who was dangerously close to giving himself a bizzare wasting sickness because he couldn't stop thinking of his own inevitable demise, I can tell you that "simply psychosomatic" can be powerful enough on its own.
The Aurum Solis reccomends that we make ourselves a magical personality to assist with magical work. Seems cut and dry enough! Honestly a big hang up of beginner students is that many are afraid of failure in magick, so they don't do it; afraid of success in magick, so they don't do it; or don't beleive that they have the ability to do magick at all! Someone else.. totally fine. Themselves? Nope. Not good enough.
So we make a new identity that we put on when we don our robe and ring, and slowly but surely become used to doing magick from the stand point of that personality. It's a brilliant strategy, really. From an energetic standpoint, you are changing what bits of your personality are getting fed Kundalini Shakti, and your old persona acts as a scaffolding for the new one you are creating. Which is much better for we householders and a totally new personality. We all know one person who has a revelatory moment of some kind and totally becomes someone else. Same life history, totally different person. That, to me, seems like needless hassle.
A gradual personality shift also slowly but surely gets you used to thinking like a mage, and thinking responcibly about your magick.
I know a few occultists who would like to be mages. Sad part is, doing magick never occurs to them. Thus, they never leave the armchair.
Is this just another case of "Fake it till you make it"? No. And I'll tell you why.
An identity shift adds new possible ability to you. If I am just a brick layer, a retail clerk, a shoe maker, a book seller, how could I of all people change my life? Easy. You stop letting external variables define who you are, and be who you want to be.
Hell, I'll do you one better: Be who you really are.
What we beleive about ourselves can easily become self fullfilling prophecy. The self help market is full of books on the subject. Hell, so is the field of psychology. Jason Miller talked about his magical idol, the great Magus Archibald Leach who forged a new personality and became a mighty leading man of the Silver Screen durring his lecture on Enchantment Magic at Crucible. Like a religious fundamentalist who refuses to believe in dinosaurs, even when confronted with the bones, we can sabotage our personalities, and our lives, or like Mr. Leach, we can liberate them.