So your basic idea is that the distant stars in the night sky can be divided up into constellations, and if you make even dividing lines between them, you can cyclically progress through them every year. Then, attribute personality characteristics or life patterns to the constellations. You can go ham with it and describe all the ways people associated with certain constellations will interact with people associated with different ones.

...Back so soon? You say the star sign doesn't really describe you well enough, that it's wrong more often than it's right? Well don't worry, we've got you covered. Just plot what sector the sun was in, AND what sector the moon was in. Take an extra sign or two, that way you have a way to claim personality traits from multiple star signs and distance yourself from anything that doesn't sound quite right about what you had before.

Have a sun sign, a moon sign, a rising sign, any number of signs! Just add more celestial positions to append agency to, and you'll be able to arbitrarily choose until you're satisfied with how well it "defines" you.