Water is quite introverted, fire quite extroverted.
Water is cautious, fire bold.
Water thoughtful, fire declarative.
Water soothes and heals, fire burns and wounds.
Water reflects light, fire emits light.
So water signs always get things more involved in thoughtful, cautious/careful, introspection. Fire signs, on the other hand always get things involved in making bold, daring proclamations.
Water contemplates the light (the truth, the reality) within itself, relative to itself, in a subjective way. So water signs promote this in the planets that occupy them: subjectivity, relativity, and contemplation. Fire, on the other hand, emits light. So fire signs usher their planets towards “emitting light” – making objective, absolute, declarations about what is true and what is not, what is right and what is not.
So fire signs are quite important when we need difficult decisions made confidently and quickly. Water signs are useless for that. But water signs are needed for developing the true wisdom and knowledge to be able to make a good decision at all. Water signs are for thought and fire for action. One symbol of this is that water silences the voice, but fire inspires alarms, noise, yelling and shouting.
Water is the element that is feminine by nature, and it therefore heals and is soothing. Water signs make their planets softer, more consoling, more sympathetic. Fire is the element that is masculine by nature – and therefore it is strong and punishing. Fire signs make planets more decisive, quick, dangerous, incisive and capable of being authorities and giving punishment to what is wrong.