What is stress?

Values and stress are associated concepts. They are associated through the concept of loss or cost. Values by their nature, concrete values such as a prized possession or a secure environment, entail the expenditure of energy, and their loss represents the loss of the energy invested. This kind of investment is basis to life. Stress is a biological and psychological condition associated with the threat of loss of acquired values and so the loss of a piece of life itself.

--Gary G. Gallopin