Photo used under Creative Commons from origami joel
There is a striking similarity between Freud's concept of the id, ego and superego and the astrological concepts of personal, relationship and universal signs. Keeping in mind that the zodiac is a symbolic representation of a single human life-time, we can see the maturation process of the signs from id to ego, and finally to superego.
The Id relates to...
The Personal Signs: Aries, Taurus, Gemini & Cancer
Freud describes the id as, guided by the pleasure principle which has a unique purpose - to get immediate satisfaction for all desires and needs. The personal signs in astrology have this same orientation and focus. The personal signs are centered around interacting directly with the environment for the purpose of self-satisfaction. Astrologically symbolic of infancy and childhood, they represent the function of the id in psychology. People with a strong personal-sign influence in their chart have a natural tendency to put their needs and wants before their desire to please others or adhere to morals. Their first instinct is to deal with things directly rather than base their decisions on the opinions of other people or on societal standards. These signs are direct and don't concern themselves with the cordialities and protocols of the relationship and universal signs. Although the personal signs are the least mature signs in astrology and the most baseline and primal of Freud's triad of the human personality, they can be amazingly powerful people. In the charts of both Steve Jobs and Bill Gates, we find Aries moons. The most immature sign in the most powerful zodiac position of the moon has given these two people the ability to push their agendas forward without undo concern for other people or greater worldly meanings that may have otherwise thwarted their progress.
The Ego relates to...
The Relationship Signs: Leo, Virgo, Libra & Scorpio
Freud describes the ego as, the component of personality that has the purpose to ensure that the impulses of the id can be expressed in an acceptable manner for the society we live in. Like the relationship signs, the ego understands that we are not alone. Everything we do affects other people. We are all part of a society of people. We want to be able to function together in harmony. Therefore we need to gauge our behavior on how it will affect others. The relationship signs gauge their behavior on the reactions they receive from other people. They are the signs most concerned with human interactions. Rather than simply taking what they want from the world, they consider how their behavior will appear to others and modify their behavior based on the opinions of others. The relationship signs represent the teenage and young-adult phases of life when relationships are highlighted and often a focus. For these signs, self-esteem is largely based on their perceived likability. On a deeper level, it's based on their ability to successfully negotiate, compromise or control other people. The key factor is their need to serve their own needs through relationships.
The Super-Ego relates to...
The Universal Signs: Sagittarius, Capricorn, Aquarius & Pisces
Freud describes the super-ego as, incorporating moral norms and values of the society we live in. Akin to the universal signs, the super-ego bases behavior on greater morals and values. Like the universal signs, the superego isn't concerned with personal needs, or with pleasing other people. It is concerned with doing what is ultimately, the correct thing. The universal signs are astrologically symbolic of adulthood, retirement, old age and finally death. They have symbolically learned the lessons of youth, so rather than taking what they want from the world or allowing the dynamics of relationships to steer their behavior, they filter their behavior through greater ideals. It isn't always pleasant for them. It requires self-restraint, and they don't always manage to live up to their own self-imposed standards. It is the burden and blessing of the wisdom of old age. Having an awareness of greater rights and wrongs can help you live a righteous life. But, it can also make you judgmental of others and it can be a constant internal struggle. With a superego conscious always whispering in their ear, the universal signs try to do what's right, but they also suffer with a depressed feeling of pointlessness and self-condemnation when they don't.