What is Tadatmya, and what role does it play in a sadhak’s life?

Tadatmya is a profound word, and understanding it can bring great clarity to a sadhak’s path.
Tadatmya is divided into two words
tat = you
atma = soul.
Tadatmya = you are my soul.
That’s the mental state of a person lost in this sansar and its objects, people, or situations.
When a person is attached to them to the point of calling it their Atma, they have established Tadatmya with them.
Without them, they cannot survive, just as one cannot survive without their Atma.
When one is in such Tadatmya, they don’t see any need to find their real Atma.
A drinker finds his happiness in alcohol.
Every time he drinks, he feels joy; he equates that with samadhi (the absence of suffering).
Of course, it lasts a very short time.
As soon as the effect of alcohol wears off, his illusion of “samadhi” also wears off, and he has to repeat the process.
That way, he keeps chasing happiness.
He has found a substitute for samadhi in sansar, and he does not see the need to go within to find real samadhi.
Of course, this is just one example, but if you really think about it, most of Sansar is in the same boat.
Attachments to race, religion, relations, money, name, fame, others’ attention, etc., are all varying degrees of tadatmyas.
Finding the real samadhi state is not difficult, but realizing and acknowledging one’s Tadatmya is.
And Priyanka’s answer is correct, stop searching; just BE, and you are in samadhi.
By searching, running, encountering, and then merging with the objects of pleasure via actions, you are creating a new (and fake) self
You drink, and you BECOME a drinker.
We never realize that by taking these steps (and keep repeating them), we have departed from our true selves.
Most likely to get lost in the jungle of samsara, never to return to BEING, unless we wake up to spirituality.