Why Shanti Mantra is recited three times?

All Sanatan prayers and Mantras from the Vedas or Upanishads are concluded by reciting 

              'Om Shanti, Shanti, Shanti '

Saying Shanti, not once but three times. 

Naturally, a question comes to mind:

Why do we say Shanti Shanti Shanti three times?

First of all  - Shanti means Peace.

Saying Shanti after a prayer means: May peace be with you.

Or May there be peace everywhere. 

But why do we need to pray for Peace? 

Peace is a natural state of everything. 

Disturbances are created either by others or by ourselves. 

Peace already exists in a place until someone makes a noise.

Peace is also a natural state of all beings - 

until it is disturbed by some hindrance - obstacles, and obstructions. 

In other words, Peace is the state opposite of pain and suffering. 

Therefore, the prayer for Shanti also means: May there be no suffering. 

Now the question is - why say it three times?

According to ancient Indian thought, there are three sources of pain and suffering.

Adhi Daivik - Natural calamities 

  - Inflicted by the act of Nature - such as earthquakes, floods, Storms, hurricanes, tornados, etc.

Adhi Bhautik - Inflicted by other beings or surroundings and circumstances 

    - such as animals, people, society, crime, pollution, accidents, etc.

Adhi Atmik - Bodily or mental illnesses.

   Problems of our bodies and minds like physical diseases, anger, frustrations, stress, etc.

These are also known as Aadhi, Upaadhi, and Vyaadhi in short. 

Since there are three types of suffering - 

therefore, to emphasize our intense desire for Peace -

we chant three times Shaanti Shanti Shanti 

- to end all obstacles, problems, pain, and suffering that originate from the above three sources.

               May peace alone prevail. 

                                     " Rajan Sachdeva "