But actual fact is that this material world is a miserable, negative place, full of danger at every step, duhkhalayam asasvatam, temporary abode of death, birth, disease and old-age, home of suffering and pain only. To come to that platform of understanding of things as they are, that is not a very common thing, and therefore such persons who attain to it, they are described as "great souls'':
mam upetya punar janma
samsiddhim paramam gatah
This verse is spoken by Krishna, or God, Himself in Bhagavad-gita so who can be more final authority? That means that anyone who has understood that the material worlds are places of misery and temporariness, duhkhalayam asasvatam, they never return here again, and because they are mahatmanah, the great souls, Krishna keeps them with Him, having qualified themselves to escape this nasty place by becoming His pure devotees.
So the point is that to make advancement in spiritual life, everything material, unless it is utilized to serve and please Krishna, must be viewed with a pessimistic eye. We are not very much hopeful for any lasting pleasure or satisfaction for our deepest cravings within this realm of gross matter.
-SPL to Lynne Ludwig, 30 April 1973