Stress is a complicated chain of interactions that begins as a natural response to events that are perceived (often unconsciously) as being threatening. The realities of day to day living often create circumstances where an increasing variety of situations are perceived as being threatening in one way or another, and where the body moves into a chronic state of "hyper-readyness".
This hyper-readiness can act somewhat like an allergic response. With each new stimulus, the body increases its reaction strength until over-reacting to small stressors becomes a habitual state of being. This, in turn, causes physical changes in the body that make it more susceptible to illness and injury.
Like a tiny crack that weakens the structure of a material as it widens and spreads, stress undermines physical health and diminishes the strength of the immune system, opening us to greater probabilities of contracting acute illnesses.
My teacher in Thailand liked to use one-word teachings. One of his favorite words was "Relax". If you follow this word into its depths, understanding what it means for mind, beliefs, worries, body, breath, muscles, expectations, relationships, desires and emotions, you will begin to see how healing it can be for stress. If "Relax" becomes a focus of each moment - learning to relax within the activities and necessities as they arise - then you will find that stress will diminish in its importance in your life.
Practices like meditation, TRE, Yoga, massage and many others can lead you in this direction. However, it all starts with intention and direction. First choose to relax. Then the way to do it will come to you.