Psychodynamic is not an easy concept to handle. But if you think of it as based on the principles of physics that we learn at secondary school, it's a little easier. So ... building on the work of Freud, Carl Gustav Jung developed  psychodynamic principles, modelling these on the first and second principles of thermodynamics. 

According to Jung, the mental sphere has conscious and unconscious parts. He thought it was divided up into a number of closed systems that interacted together.

These mental systems take in energy from the environment (you can think of it as petrol and air going into an automobile) and so the person is energised. But the way in which these inputs get distributed around the psychic systems looks like this: 

The Principle of Equivalence assumes that if the amount of energy in your psyche decreases or disappears, then the same amount of energy appears somewhere else. Take an example. Anxiety can be like spinning your car wheels. Energy ends up as vibration and noise. Through psychotherapy, you have the ability to heal yourself through finding out what has happened and rerouting energy elsewhere. Your energy can be positively relocated.