Everyone is trying to be happy, sukham asyatmano rupam sarvehoparatis tanuh: when the living entity is in his original spiritual form, he is happy by nature. There is no question of miseries for the spiritual being. As Krishna is always happy, the living entities, who are His parts and parcels, are also happy by nature, but because of being put within this material world and forgetting their eternal relationship with Krishna, they have forgotten their real nature. Because every one of us is a part of Krishna, we have a very affectionate relationship with Him, but because we have forgotten our identities and are considering the body to be the self, we are afflicted by all the troubles of birth, death, old age and disease. This misconception in materialistic life continues unless and until one comes to understand his relationship with Krishna. The happiness sought by the conditioned soul is certainly only illusion, everyone is trying to be happy because, as explained in the previous verse, sukham asyatmano rupam sarvehoparatis tanuh: when the living entity is in his original spiritual form, he is happy by nature. There is no question of miseries for the spiritual being. Just as a deer, because of ignorance, cannot see the water within a well covered by grass, but runs after water elsewhere, the living entity covered by the material body do not see the happiness within himself, but runs after happiness in the material world.
Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Seventh Canto, Chapter 13 – Text 28