The Fixed Quality, or modality, represents the center of each season and the most typical expression of the season it is a part of. When in the Fixed Signs, the Sun appears to be moving at an average rate of speed, which is approximately the same for all four signs in the group.
This phenomenon gave the ancients the sense that the Fixed Quality is the most stable of the three, and the concept stuck, because it, like the people whose horoscopes are dominated by the Fixed Quality, is reliable and sensible. The Fixed Signs are Taurus, Leo, Scorpio, and Aquarius.
People whose charts are dominated by the Fixed Quality tend to be set in their ways. Whether their characters are practical, passionate, mysterious or unconventional, because of the elemental nature of their signs, they will develop a solid personal style. With Fixed people, it may be hard to tell the book by its cover.
Whatever the Fixed person finds themselves involved in, they are usually committed to it. Whether this happens to be loyalty to a cause or the determination to write a great novel, they are more likely to stick to it than people dominated by either of the other two modalities.
A Fixed person is more likely to finish what they start than any other, and is more likely to express themselves through their deeds than their words. When they are hard on themselves, it's because of not living up to their own expectations, but they are usually too practical to overestimate their abilities.
At the same time, the Fixed Quality can add a note of stubbornness to the character. Once their minds have been made up, it's almost impossible to change them. This characteristic also makes Fixed people very self-reliant; "if you want a job done right, do it yourself" is a typical Fixed expression.
Because the Modalities or Qualities describe ways in which the Elements function, they really aren't factors in relationships on their own. They do however, represent part of the nature of the Zodiac Signs, where the Qualities and Elements combine.
If you have an interest in a Fixed person, you'll find them to be quite reliable. Even when engaged in quirky or eccentric behavior, they will direct that behavior to a practical purpose. Many inventors or crafts-people are born in the Fixed Quadrature. No matter what Fixed people do for a living, when at home, they can be rather handy.
The Fixed person is generally a quiet type, and doesn't tend to waste words when they do speak up. They are usually concerned about how they represent themselves; they want to be seen as reliable and truthful, and don't like to make mistakes. They almost always honor their commitments, and generally stand up for what they believe in, even if their beliefs aren't part of the conventional wisdom.
Above all, people born with a dominance of the Fixed Quality seek security. It doesn't matter whether that security is physical, emotional, intellectual, or material, they like to establish themselves in ways that they become as protected as possible from having to be distracted by unexpected changes in their lives or their relationships.
In order to understand the meaning of the Fixed Quality better you can read our article on the Fixed Signs or read about the individual signs that have this quality: Taurus, Leo, Scorpio, and Aquarius.