The quest to know self is by another words to reach the supreme. Quest to know self happens only when we lose the word "self". The self or "I" merges with supreme after which there is no more "I". This union is called yoga/yogam. The differentiation is lost and there is only one thing that exists at this state which is him.
Vaasi, Kriya and other practices are the paths, but the end is non-duality which is elimination of ego or the I in us. Gita hence says everything starts and end in me. I'm the purusha (paramatma) in you.
The removal process of "I" is similar to death. This is because we have conditioned to everthing as I, my family, my god, my...everything. It is to recondition us completely to a point that "you are him" by thoughts and actions and go by the truth which means everything is of his. After a point there is no "you" and only him. It happens when you do your activities and surrender without expecting the result. Then you finally see him after which there will be no more "I"
A small tale to describe it better.." as heard on a TV show"
Once there was a highly learned man who came to Shirdi Sai to clarify his doubts with him. Apparently all intellects learn a lot of books. This gentleman had gone through various books on gita.
However Sai gave this gentle men a perspective which took him by highest surprise. So the gentle man asked Sai where do I get these kind of meanings for Bhagavad Gita like most clever people do. Sai smiled and told him "I'm the one who wrote it...". So at higher level it is just him which is the oneness. If you know that, there is no more "I" or "Self Intellect" there
It is the universal intelligence which one will never understand until the "I" is stripped out