What is the role of stress in the process of behaviour change (lifestyle)? Clarification: I am specifically looking at lifestyle behaviour change.

I suppose that stress can influence the process of behaviour change in many different ways. One would be just the changing of behaviour itself that will cause stress. However, stress may also cause behaviour change (say, one may initiate behaviour change because of the diagnosis of diabetes). In the end, the aim is to feel better with your new healthy lifestyle, which should result in lower stress levels.
This is my thinking based on a (non-literature-supported book) that I read, and now I am looking for scientific evidence for any of the influence stress may have in the process of behaviour change.
Also, any other theories as to how stress may play a role in the process of behaviour change?
If you suffer stress or anxiety, a chemical warfare gets underway within the body and if not dealt with effectively, everything starts to self-destruct.

Stress and anxiety will activate the Autonomic Nervous System and cause Cortisol levels to increase to get us ready for conflict and prevent wind-down, which in turn will lower Serotonin levels. The low levels of Serotonin will affect our ability to have a restful sleep and because Serotonin helps to relay messages from one area of the brain to another, the low levels will also affect the ability of your brain to act on information received as efficiently as it should. (WebMD 2015)

Noradrenalin is affected by stress and anxiety, and noradrenalin is another “feel good hormone”, which when imbalanced will affect many aspects of our system, one of which is energy levels causing us to feel lethargic and not wanting to bother with life.  Dopamine and endorphins are other happiness hormones which are affected by stress and anxiety affecting our ability to enjoy things, therefore it is no surprise that it can lead to depression.

Endorphins trigger a positive feeling in the body, similar to that of morphine. For example, the feeling that follows a run or workout is often described as "euphoric", which indicates the endorphine boosting effects of exercise. That feeling, known as a "runner's high," can be accompanied by a positive and energizing outlook on life.

As high levels of Cortisol and high levels of the "feel good hormones" cannot coincide together, the increase in endorphines will in turn lower Cortisol levels and therefore increase the Noradrenaline, Dopamine and Seratonin levels boosting the positive outlook on life.