In Yoga Sutra 1.35,Patanjali talked about shutting down mental processes to do away with confusion,indecision and worry.
In Yoga Sutras 30 to 34,Patanjali explained about the effects of a wandering Mind.
Lord Krishna speaks of this state of confusion and indecision in the Bhagavad Gita, in Chapter 2.
When the mind is confused,with constant,relentless bombarding of Stimulii,the Mind is bewildered at the mountain of information received.
Buddhi,Intellect,which is a higher Plane than Mind,when confronted with making a Value decisions like Correct or Incorrect,Right or Wrong,also dithers.
This has to be corrected as the sensations that lead to emotions distort facts and misguide the ability of the Intellect to judge and decide.
This is what Krishna says in the sloka,Chapter 2,
‘Krodhaath Bhavathi Sam mohaha
Sammohaath Smriti vipramaha,
Smriti Dhwamsaath Buddhi Naaso,
Buddhi Naasaath Pranasyathi’
Out of Attachment arises Anger,
Anger breeds and fuels Intellect dithers,
When Intellect is destroyed,incapable of making right decisions,one is destroyed.
In Yoga Sutra 1.36,Patanjali offers a way out of this.
When we perceive,we have the objects we Perceive and our Impressions of them in the Mind.
The Objects do not change from time to time.
It is our interpretation of them atca particular point of time changes.
So what needs to be changed is our perception of Objects.
This is effected by the Mind and passed on to the Buddhi,Intellect,which thereafter can make the Right Decision.
So to shut down the external Objects,Patanjali adises one to Concentrate on a source of Light.
This is first step in Concentration,called Dhyana.
Here you are aware that you are concentrating and that there is an Object being Concentrated upon.
You are aware of both.
Next step is Dharana,when you forget that there is an Object you are concentrating upon, so immersed are you in your concentration.
The next and final step is Samadhi,where you and the object mergevand there is no Duality.
Patanjali Sutra 1.36 ,with Swami Vivekananda’s commentaru below.
36. णवशोका वा ज्योणतष्मती ॥ ३६॥
vishoka va jyotishmati
Or (by the meditation on) the Effulgent One which is
beyond all sorrow.
This is another sort of concentration. Think of the lotus of the heart, with petals downwards, and ruunning through it the
Sucumna; take in the breath, and while throwing the breat out
imagine that the lotus is turned with the petals upwards, and
inside that lotus is an effulgent light. Meditate on that.