सर्वगुह्यतमं भूयः शृणु मे परमं वचः ।इष्टोऽसि मे दृढमिति ततो वक्ष्यामि ते हितम्॥
sarva-guhyatamaṃ bhūyaḥ śṛṇu me paramaṃ vacaḥiṣṭo ‘si me dṛḍham iti tato vakṣyāmi te hitam
Word by word
The verse says
Hear my highest word again, the most secret of all. You are very dear to me, and that is why I will tell you what is good for you.
In plain words
And then he speaks again, after handing over the decision. He is not finished.
The reason given is not that Arjuna needs more argument. It is iṣṭo 'si me dṛḍham - you are dear to me, firmly.
That is the reason. Not the logic of the case. Affection.
Where you've felt this · in friendship
A friend has given you his honest opinion and you have said you are going to do the other thing. He says fine, and means it. Then at the door he turns round and says one more sentence, which is the thing he actually wanted you to hear. That sentence is usually the real one.
Going deeper
Speaking again after the decision has been handed over is the opposite of pressure, and the reason given is what makes it so.
If the aim were compliance, saying more after yielding the choice would be a technique, and a well-known one. What is given instead is a reason that has nothing to do with winning: you are dear to me. The further words come from attachment to the person, not to the outcome.
That is a distinction most of us handle badly with people we love. We present concern and deliver pressure, and the two are hard to tell apart from the receiving end. The test is whether you would still say it having fully accepted that they may do the other thing.
And this is the first time in the book that Krishna gives affection as his reason for teaching. Seventeen chapters of argument, and the last stretch opens by saying that the reason for all of it was that he is fond of him.