A mortal, having heard and fully grasped this, and having realized through discrimination the subtle Self, rejoices, because he has obtained that which is the source of all joy. I think the abode (of Truth) is open to Nachiketas.
The Scriptures give three stages in all spiritual attainment. The aspirant must first hear about the Truth from an enlightened teacher; next he must reflect upon what he has heard; then by constant practice of discrimination and meditation he realizes it; and with realization comes the fulfilment of every desire, because it unites him with the source of all. Having beheld this, a man learns that all sense pleasures are but fragmentary reflections of that one supreme joy, which can be found in the true Self alone. Yama assures Nachiketas that there is no doubt of his realizing the Truth, because he has shown the highest discrimination as well as fixity of purpose.