Susceptibility represets an individual's tendencies, both their strengths and their weaknesses. It is concerned part of a person's overall constitution and vitality or healing ability. It is affected by past and current diseases, injuries, beliefs and thoughts. For example, if a person believes that disease and a lower level of health comes with age, a decrease in healing potential might be more a reflection of this belief than their actual health status. If a person believes that they are likely to suffer the same symptoms and diseases as their parents, it is more likely to happen. The aim of maintaining health is supporting and maintaining areas of strength, and adjusting and balancing for areas of weakness. 
- Lloyd Iva (2009) The Energetics of Health, a Naturopathic Assessment Elsevier.