He, who has got large possessions in his house, is troubled, wherever he goes, with the anxiety that they may be lost or burnt or stolen. Then there is a great pain in being born: the dying are afflicted by the tortures of Death and again by the pain of passing into the womb. Fancy, there is not the least pleasure in the embryo state; you must then admit that the world is full of miseries. Verily I speak unto you, that in this ocean of the world infested with many miseries Vishnu is your only stay.

In plain words: Prahlada says rich people always worry that their things will be lost, burned or stolen. Being born, dying and entering a womb again are all painful. So the world is full of suffering, and Vishnu is the only safe shelter in it.