In the previous quotes that I used of the Buddha discussing the emptiness of the self, he was mostly referring to the body, the physical manifestation of the self. But obviously, there's more to the self than mere bodies (isn't there?), so what about the ego, the personality, the psychological persona?
The Buddha did address the emptiness of the ego-self. In analyzing the self, the Buddha determined that it is nothing more than the sum of five conditions, which he called "Aggregates" (skandhas). Bodily form is only one of the Five Aggregates; the others are often referred to as feeling, thought, impulse and consciousness. Whenever these five conditions come together, there is something that conceives of itself as a "self."
To illustrate, imagine a body, any body. Since the body includes organs of sensual perception, it experiences feelings, the second Aggregate. The brain, the organ of cognition, sorts through and analyzes these feelings by the Aggregate of thought, and accordingly reacts to them (impulse). Consciousness, the fifth aggregate, is aware of all of this (body, feelings, thought, and impulse). When all Five Aggregates are present, then there exists a sentient being that considers itself, well, a self, and when any one Aggregate disappears, the self also disappears.
Each of these Aggregates are impermanent and interdependent, and because these Aggregates are impermanent and interdependent, we have an impermanent, interdependent self. Our suffering is caused when we cling to the the delusion that the self is something permanent and eternal, and we therefore come into conflict with our actual impermanent, interdependent nature.
"Imagine," the Buddha once said, "a mountain torrent, rising from afar, swift-flowing, and on both its banks grasses overhang the stream. Suppose that a man is swept away by that stream and clutches at the grasses, but they break away and owing to that he might come to his destruction. Even so, brethren, the untaught folk regard the body as the self, or the self as having a body, or the body as being in the self, or the self as being in the body. Then the body breaks away, and owing to that they come to their destruction. So, too, with feeling, thought, impulse, and consciousness."
The concept of the Five Aggregates has been refined over the centuries, and in Zen it has come to take on more of a psychological aspect. In his translation of The Heart Sutra, the Five Aggregates are ably described in their Zen context by Red Pine as follows:
Form (Rupa) - The first Aggregate is more than just the body, but all form. In fact, according to Red Pine, “Form is not the material world. It is simply the outside world, in contrast to what we presume is an inside world.” Like the famous black-and-white picture that at first appears to be a vase, but upon closer inspection looks like two faces in silhouette, the form of the outside world defines the inside world ("I am that which is not others"), just as the outside world is itself defined by the inside ("Others are that which is not me"). Hence, in Zen, form is defined by emptiness and emptiness is defined by form.
Sensation (Vedana) - “This is not the same as sensory input," Red Pine writes, "but rather the evaluation of input, which the Buddha rarely described in any more detail than positive, negative, or neutral. For the most part, our experiences are neutral and ignored.” But we do take notice of that which gives us pleasure or that which might pose a risk.
Perception (Sanjna) - Perception is what enables us to classify our sensations as positive, negative or neutral. It supplies the means that allow us to manipulate our sensations, so that we see what we want to see and don’t see what we don’t want to see.
Memory (Sanskara) - Memory supplies us with the templates that perception applies to sensations and form. It embraces all of the ways we have dealt with what we have experienced in the past and that are available to us as ways to deal with what we find in the present. It includes habitual behavior patterns such as intelligence, belief, shame, confidence, indolence, pride, anger, envy, sloth, repentance, doubt – anything that might provide us with a prefabricated set of guidelines from the past with which to perceive and deal with the world, both inside and out, as we experience it in the present.
Consciousness (Vijnana) - Consciousness refers to the faculty of mind in general, the ability to be aware, aware of anything, but always of something - form, sensation, perceptions, memories, and of course, a “self.” To discuss or analyze consciousness would be like the hand trying to grab the fist. Buddha always discussed consciousness in terms of a sense, hence, sight consciousness, hearing consciousness, thought consciousness, and so on.
Consciousness has evolved as a sort of radar to allow organisms to protect themselves - without awareness of a self, there would be no conception of something to protect, and an unprotected organism wouldn't last long in Darwinian evolution. There are strategies for survival other than the "fight or flee" option available from consciousness, but if we identify with our consciousness, with our radar system, then of course we are going to fell paranoid and under attack all the time.
So, putting all of this together, we define our physical selves based on an awareness of the outside world - we are that which is not something "out there." We are aware of that "outside world" due to sensory perception, most of which is ignored other than that which might threaten us or satisfy some need. We manipulate those sensations and sort the sensations into positive, negative or neutral using our perceptions, which are learned and stored in memory. And because we are conscious of all this, that consciousness, in turn, considers the forms of the outside world "other," leaving the emptiness defined by the form as the "self."
And yet we feel that the "self" - the one seeming constant in our lives - is somehow permanent and immune from change (I've never been someone else), and it's the outside world that is ever changing and dynamic and impermanent. It was this misconception that the Buddha set out to dispel in order to end our suffering. Therefore, in Buddhism, it is taught that what we call the "self" is in fact, impermanent, interdependent, and empty of any independent existence. It is even said that there is, in fact, no such thing as "self."
And yet the elderly tenzo said to Dogen, "Others are not me."