Chapter 6 Dhyana Yoga Verse 12
Shloka

Sukhamaatyantikam yattad buddhi graahyamateendriyam;
Vetti yatra na chaivaayam sthitashchalati tattwatah.

Translation
When the Yogi feels that infinite bliss which can be grasped by the pure intellect
and which transcends the senses, and, established where in he never moves from the Reality.
Interpretation
Lord Krishna here talks about the feelings of a Yogi who has experienced the deep meditation. He says that a yogi who experiences the bliss of meditation with pure intellect can only experience the reality. Reality here means Brahman. This intellect that he acquires is because the yogi transcends all his senses while meditating and establishes himself in a positions which is beyond the grasp of any of the senses. Such a person gets to know what is real and once he understands the reality he will never move from that position of reality.
Extending Interpretation to Mankind’s Life!
The key words that one has to understand here are infinite bliss, pure intellect, transcending of senses and sticking to Reality. First let us understand what exactly is the reality. Reality can be explained through a phrase from upanishads which says “Brahma Satyam , Jagat Midhya”, which means only truth in this World is the Brahma and everything else is an illusion or maya. Brahma here means God. So God is the only real thing and all the other things are illusions. When you reach Brahma you remain still there and you also experience infinite bliss. It is because the person who sees reality does not need to see anything else and that is the point of infinite bliss for him.
The other two things we need to understand are the pure intellect and transcending of senses. These two things have a strong link to the eternal bliss that I mentioned previously. Here we have to understand that a person can only transcend his senses with his intellect. The knowledge he acquires takes him into situations where he understands how senses are binding him and are hampering his spiritual progress. Once he understands that he will try to transcend the senses by acquiring more and more intellect and that in turn takes him to the reality of Brahman.  Once he gets that experience he will feel an eternal bliss which is nothing but reality. This is how a yogi meets the reality.