Though there may be more aspects to balance than this, I know of two aspects that I will discuss now.
The first is the four aspects or ourselves that we need to develop and also listen to. This I learned from listening to an Aboriginal elder. Many of the First Nation's peoples of Canada have the concept of a medicine wheel. I am certainly not an expert in this, but this is what I understand of it. There are four parts of the medicine that can represent different things. They could represent the four cardinal directions, north, south, east and west. They could also represent the four broad races of people, white, black, red, and yellow.
The four parts of the self are mind, heart, body, and spirit. For Western audiences that believe the heart is just a muscle that pumps blood around the body I shall rephrase these a bit as reason, emotion, spirit, and body. These are four parts of ourselves that we need to develop and listen to and have balance between.
For a long time I was out of balance. I read many books, was quite cerebral and lived mainly in the reason part of myself. I had, in particular, lost touch with my body. I needed to learn to exercise more so that I would be able to listen to my body. After doing this a bit I realized my body was full of toxins. I have acne all over my body which I believe, and which naturopaths have told me, is toxins from inside my body leaching to the surface.
I most certainly am not in balance between these four aspects of myself right now, largely due to a lack of time. I would really like to meditate and exercise more than I am. I just can't find the time at the moment. Furthermore, since I currently need a full-time job to pay the bills, but my passion lies in building my own Internet companies, I will essentially have two full-time jobs for the foreseeable future. In order to accommodate this I will choose to be out of balance and focus intensely on the rational - only paying attention to the other aspects of myself as much as I need to in order to sustain my ability to pursue my goals.
The second aspect of balance that I know of is the balance between the mundane and the meaningful. The mundane is the need to pay the bills, make a paycheque and pay the rent or mortgage, feed one's family and pay the phone bill. It also involves filling out boring tax, insurance, or other types of forms, and taking care of necessary chores, like washing the dishes or taking out the trash. The is a necessary aspect of life and it is also useful in that it keeps us grounded.
The other side that we need to pay attention to is the meaningful. Essentially, what are you doing with your life that gives you a sense of meaning? When you are 80 and look back on your life, how will you be able to complete the sentence, my life was worthwhile because I did ....?
Some people get this meaning through their careers. Some people are healers, such as doctors, nurses, therapists, etc... Some people are protectors, such as police officers, military personnel, or fire fighters. Some people get this meaning through taking care of their families. Other people volunteer. Some are lucky enough to have meaning in multiple aspects of their lives.
I think that many people in our society are out of balance in this. There are many who are primarily concerned with the mundane only. Can I get a stable job to pay the bills and forecast how I will pay the mortgage? At the extreme people in this mode have a job that they see as pointless and meaningless and are not emotionally involved in. Then they go home to do nothing but sit semi-comatosed in front of the television because that provides escape to a more interesting and meaningful fantasy life that they subconsciously believe is not for them. This is perhaps not the best way to live. Essentially if you are living this life then you are a zombie - a member of the walking dead.
The opposite extreme are the starving artists. I personally believe that art (including music, poetry, movies, and novels), when it is true art, is exceptionally important. It can cut straight through the rational mind and speak directly to the emotional mind and even the soul. Having said this, making great art that no-one but you ever sees and then not being able to eat more than once every two days is perhaps not the best life either.
I myself have focused a bit too much on meaning in my life at times. I went into physics in order to investigate the fundamental nature of the Universe. I went into public administration so I could enter government and save the world. I have quit jobs that paid a decent, stable salary because I thought I was completely useless there. I am hoping now to monitor my finances more and get them under a bit more control now. I still am pursuing meaning. I do want to make the world a better place. I have just realized that I need a stable income while doing this.