Preface
There are many different ways to perceive, utilize, and benefit from energy. What I offer here is one of many ways. Indeed when I do other kinds of activities I perceive of and work with energy in quite a different manner. What follows is my experience of energy while performing Aikido over the course of more than twenty years. Certainly there are likely to be many other Aikido practitioners that would explain their experiences and beliefs in a manner that is somewhat different than mine. I offer you here, one experience, my experience, and thus all that I say is part of my belief system, and not at all necessarily THE truth.

Aikido
Aikido is a Japanese martial art, and it does not have an attack form. We do not kick, punch, or in any other manner, attempt to hurt our opponent.

The meaning of Aikido:

"Ai" To gather or harmonize.

"Ki" Universal life force/energy.
This is the energy that we share with nature and all living beings.

"Do" An artful path of discovery.

"Aikido" An artful path of discovering how to gather and harmonize the energy of the universe.

When we sense and move with the energy that is manifesting throughout the universe we find that we have a greater ability to live a life that is healthy and fulfilling.

"Ki"
In Aikido we believe that all human beings utilize and share a common energy source (ki) that helps to run and maintain our environment as well as our individual human systems. We believe that since we all share a common energy source, that in some important way we are all truly members of the same family, and truly sharing our lives with all of nature. We do not have an attack form in Aikido, because attacking an opponent would be like attacking a family member that you love. Attacking an opponent would also be like attempting to damage the flow of Universal energy in the world, and such acts are likely to have many far reaching consequences.

In the Japanese language words that use the concept of "ki" are common.
"Gen-ki" means "root energy" or one's "personal health".
"Ten-ki" relates to "heavenly energy" or "the weather".
"Hon-ki" relates to "original energy" or "the truth".
"Yuu-ki" relates to "brave energy" or "courage".
"Ki o tsukete" means "attach your energy to what you are doing, or "be careful".

The origin of ki?
Where does ki originate from? In Aikido the answer is poetic in nature rather than scientific. It is suggested that ki was "born" at the same instant as the rest of the universe, and that we are all born from the ki of the universe. Ki is considered to be an energy that we all have equal access to. It is an energy that courses through our system if we do not restrict it. In Aikido we believe that excess tension physically and emotionally, fear, hate, greed, and anger, all cut us off from the universal source of ki. Our daily practice involves working at maintaining a balanced state physically and emotionally, and indeed, practicing ways to cultivate physical and emotional balance is much of what the study of Aikido is about. In Aikido physical and emotional balance are meant to be two sides of the very same coin. Physical balance helps to engender emotional balance and health, and vice versa as well. Often in my professional work with individuals I find myself first addressing the clients physical balance when they come wanting to resolve emotional issues, and I do the reverse as well. I often first address or explore how emotional imbalance might lead to the physical difficulties they are experiencing.

"Ki signature" mind, spirit-Energy manifests as spirit, spirit manifests as mind
Energy manifests within each individual as spirit, spirit manifests in each individual as mind. In some way that is a mystery to all of mankind, the freely available energy of the universe is transformed by each person into one's own unique "ki signature", spirit, mind. No two people have the same exact "ki signature", just as no two people have the same exact written signature. No two people have the same exact spirit, no two people have the same exact mind. The unique way that we each take in, utilize, and expend energy, can be considered to be our "ki signature", mind, or spirit. Each person starts with the same source of energy, and manifests this energy in a way that will never exactly be duplicated by any other human being.

Thought, body structure,and movement, shape the flow of ki, into spirit/mind
Think of the freely flowing water of a powerful river that comes upon a series of fairly large rocks spread out across the river bed and extend up beyond the water's surface. These rocks affect the flow of the river but they do not change the nature of the water itself. Ki flows through the river bed of our brain and body. Our thoughts, body structure and movements, are like the rocks in the river bed. These are the main elements that shape ki into individual mind, or spirit The flow of ki is uniquely transformed by each human being, but the nature of the ki itself, is not altered in the process. Just as the pattern of rocks spread out along the river bed is never exactly duplicated in any other place on earth, the pattern of our thoughts, body structure, and movement is also never exactly duplicated. All mind is similar, but no two minds are exactly alike.

A heartfelt understanding of the nature of our spirit will help us to create a healthy alignment of our thoughts, body structure, movements, and actions. When every aspect of our self is fully aligned we have a much greater ability to think, feel, and act in accordance with what is best for us in any given moment. We are better able to adapt and change in a manner that is supports the well being of our entire self and our surroundings.

The misnomers of "mind-body" and "mind and body"
A definition of "mind" that I often use it in my work, is the following:
"Mind is a dynamic, self-organizing, creative system, capable of overcoming physical and temporal constraints. Mind uses and manufactures energy in order to support the self and one's surroundings, trade information, and adapt to change."

When considering this definition of mind, we can say that mind manifests equally in the body and in the brain in the skull. Because of this I believe that the terms "mind-body" or "mind and body" as used in the Western world, are somewhat missing the mark and tend to lead to a certain degree of misunderstanding. If you ask a Japanese person to point to their mind, usually they will point to the area of their heart, or they will point to their lower abdomen. If you ask the average Westerner to point to their mind they will point to their head. This is why I think the terms "mind-body" and "mind and body" were developed in the Western world. I believe that the average Western person thinks of the term "mind" in relation to "thinking" or "thought". Oriental philosophy considers "mind" to be immanent in both the body and the brain. In Aikido we say that we practice in order to calm the mind, by coordinating our thoughts, the actions of our body, and our breath. Or we say that we practice in order to further empower and actualize our mind by coordinating our thoughts, physical actions, breath, and spirit.

When looking to calm our mind we give our primary attention to calming our breath and our heart beat, which will tend to lead towards a relaxing of our musculature and a slowing down or cessation of our internal dialogue. If we calm our body we will tend to calm our cognitive thought processes. Calming the mind can also be accomplished by giving primary attention to the speed, rhythm, and tone of voice of our internal dialogue. If we calm our cognitive thought processes we will tend to calm the body. When we calm both our cognitive thought processes and our body, then we calm our mind. Cognitive mind and somatic mind are part of a recursive feedback loop. You can't affect one without affecting the other.

Practice
A Seishindo practice that relates to what you have been reading is entitled "Heartbeat Breath - Calming Breath" practice. Please give it a try.