KATHOPNISHAD CHAPTER 2 SHLOKA 21

                                               आसीनो दूरं व्रजति शयानोयाति सर्वतः । 

                                               कस्तं मदामदं देवं मदन्योज्ञातुमर्हति ॥ २1

                             ASINO DURAM VRAJATI SHAYANO YATI SARVATAH|

              KASTAM MADAMADAM DEVAM MADANYO DNYATUM AHARTI ||21

WHILE SITTING, IT CAN GO FARTHER  AND WHILE SLEEPING IT CAN BE EVERYWHERE. 

  WHO ELSE (OTHER THAN ME)CAN KNOW THAT WHICH CAN BE HAPPINESS OR NOT||21

     This one is again a talk from God of Death . This one has been interpreted differently also. So my understanding which is related to the previous SHLOKAS, is that God of Death continues to talk to Nachiket. So in this one he is describing the ATMAN or GOD or the ultimate CONSCIOUNESS . So the YAMARAJ is telling Nachiket, The consciousness is pervading everything  and so it is far even when the physical body is sitting and still and not moving . When the physical body is sleeping the consciousness is EVERYWHERE. So HE is telling that the physical body is not the ATMAN and the physical body has limitation as is said in past -PRADESH-KAL-CASTU which is location-time-identity or Object. So when one looks at anything it has these 3 limitations. The computer that I am writing this blog. It is on my table in may home . So it is not in library or in your house or not even in my family room. This is limitation by place  and it is here now  and may not be there tomorrow  and was certainly not there 2 years ago - this is limitation by time  and it is computer and not a glass or pen etc. is the limitation by VASTU or Object or identity. But we mortal being are not aware of THIS ATMAN OR CONSCIOUSNESS as long as we have physical body and we think this is the SELF. So the Lord of DEATH is telling that who else HIMSELF or DEATH know this fact or the ATMAN. The death destroys the physical body  and then we still have existence and so DEATH is the teacher who knows about this fact. The part about happiness or sorrow - I feel that it is related to DEATH of human body also. The people who have lost  love one , will be very unhappy  and the person whose physical body died can be happy or unhappy . The other meaning is that when THE SAME SELF is limited to PHYSICAL BODY due to ignorance , it can be happy at one time  and unhappy at other time as now we are talking about pleasure  and happiness of physical body .