At different points in our lives we dispense this soul energy in various ways--at the beginning of a new relationship, we invest a large chunk in our lover: discovering who we are together, exploring the feelings they inspire in us, and building a foundation of soulful connection so that eventually it is not as exhausting to co-exist. Other times we spend our energy on a passion; training for a marathon requires not only physical endurance, but a dedication of soul. We cannot commit to a goal without pooling our emotional energy and focusing on the end result.
However, I believe we have a finite amount of both types of energy; there is a limit, a point where we simply become exhausted, so it is important to learn how to spend your energy. Life is at it's best when we have found a way to invest our energy in different pursuits: family, passion, love, learning, friends, etc. In order to feel completely centered in life, we need to become efficient managers of our spiritual energy, to know when we can spend a little more in one area, and when we need to pull back and spend a little on ourselves. In essence, this is my attempt at a somewhat scientific explanation of the need for balance in one's life.
Ironically, it can be exhausting just trying to figure out where to spend our energy. But when we do get it right, the result is a blissful hum that resonates beyond our physical existence.
The result is peace.