Wow this topic exploded, it tends to do that when it's a subject about astrological signs. We study the "round art" (astrology) and without opposites we would be studying a semi-circle, which is incomplete and doesn't encompass the whole reality of life, we have no opposite sign to compare how our natures can become balanced, obvious but true.
One usually can't exist without the other, war/peace or individual/group. I find the signs that follow us exhibit an opposite nature as in Leo pride and self-expression and Virgo's humble nature. Planets exhibit opposite natures (Jupiter and Saturn). According to psychological astrology air and water are opposites in nature and Fire and earth.
But since this subject concerns only opposite signs, I do think we balance each-other out, the trines agree with each-other, the squares create the most friction, sextiles can harmonize and are less flowing.
The Aries pioneering, assertive identity works well when there is compromise and consideration, it's not until a sign reaches it's opposite that we learn how we can best balance our energy. From the very first point of "Identity"

all the way to

, do we realize that our actions (Aries) have consequences upon other people (Libra). This is from a broad perspective.
The two signs of "identity" and "self expression", Aries and Leo are two self-expressive fire signs, and their opposites Libra and Aquarius relate to other people through the public, or in a personal relationship and represent the group, and friendships etc. Libra can learn about self-direction and assertiveness from Aries. Aquarius with their detachment and intellectualism can learn from Leo a sign that rules the heart and his basic need is to be an individual, with warmth, and self-expression (shining in his individuality) - and not getting lost in the crowd. Leo can need all the attention and approval, and this can be balanced by a broader perspective and looking at the needs of the group, and he can learn detachment and objectivity (Aquarius). All the opposites share similar modes of action whether mutability or fixed or cardinal natures. They can elementally and mutually work together and often they have a lot in common.
Cancer and Capricorn are both focused on security, yet, Cancer is orientated toward the family, nurturing and emotional well being. Capricorn is often the bread winner, and authority, and is dependable when it comes to material support. However, both signs have traditional values, and archetypally they are seen as the Mother and Father image. The family needs both of these signs to function and feel supported on both levels, too much materialism and worldly objectives leave the family's emotional needs neglected. Too much taking care of others and emotionalism, can lead to dependency. The whole cardinal square can be activated in this whole scenario to be honest. Your own identity

trying to form with others

. We also have the family's needs

and your own contribution to society, and responsibility

. I guess it's not called a cardinal grand cross for nothing. I have a headache now... too much stress.
You notice when a relationship ends (Libra), and your back to focusing on your identity (Aries), and you no longer have another person to consider, and you can do what you like in your own home. You can paint the whole house pink if you want (bad idea) with no objections, or having to ask "do you like this colour, because you have to live with the colour too" or "what about this settee" etc. It's freedom of individual expression, you can do what you want. It's like that when you leave mum and dads home (Cancer - Capricorn). When I first moved out I was like "Yes I can make my own rules now, more independence (Aries), until you meet someone (Libra) and have children and then you are the "Mum and Dad" and your kids can't wait to move out and get away from you

. Isn't life fun...
Blah blah blah.
