The fire in your heart is thirst..
Thirst exists till real knowledge has not happened. I use word happened intentionally because this knowledge is not attained it happens. It happens because it is not knowledge at all in the senses we refer this word to
In the cloudy day we feel sun is not existing but the fact is sun is already there and very much available. The presence of cloud is prohibiting sun to happen to us. So someone is thirsty means the knowledge has not happened yet. The person may be knowledgeable but not enlightened. This knowledge itself removes all thirsts, all darkness, all desires..
More accurately worded answer will be "search" is mind. It is not that it is search of mind. Mind in itself is a directionless activity and this aimless wandering we feel as search. This is restlessness which makes us feel uneasy and this unease is indicator of the fact that mind still exists.
You must have read about brownian motion. Atoms continue to wander here and there aimlessly. If a philosopher looks at this motion he will attach a theory to it. He may postulate this movement tells that atoms are searching for something.
But the fact is until these atoms are brought to absolute zero temperature this motion shall continue. This continuous wandering, brownian motion, restless motion of our mind indicates we are not reached "Absolute" so far.
All thesearch of man is to drop the mind. This whole futile activity of mind is about attaining the state of complete rest.
In the field which exists between atman and parmatman this poor mind is trapped and is continuously turmoiled.
It tries to survive and attain peace which is completely impossible. Its freedom can happen only in its death.
But the mind fears its death and coninues to escape. In its escape it creates state of turnmoil.
When we become aware of this fact – we start moving in the right direction.We do not search for anything. We know that between the happening and current existence only mind is coming. So we just allow this mind to disappear.when zenith of awareness and absolute attentiveness is achieved.. that particular moment mind disappears, the union happens!The search is mind. The thirst is synonym to search. So the question is not who is thirsty, the question should be what is thirst and how to get rid of it.The above is the direction in which we can attain that contentment where all thirst disappears, where all search is over, where we are united with the ultimate beauty of param, the absolute.