Śrī Caitanya Mahāprabhu has declared every living entity to be an eternal servitor of the Supreme Personality of Godhead. This is the constitutional position of all living entities. Just as a dog or servant is very satisfied to get a competent, perfect master, or as a child is completely satisfied to possess a competent father, so the living entity is satisfied by completely engaging in the service of the Supreme Lord. He thereby knows that he has a competent master to save him from all kinds of danger. Unless the living entity comes to the guaranteed protection of the Supreme Lord, He is full of anxiety. This life of anxiety is called material existence. To be completely satisfied and devoid of anxiety, one must come to the position of eternally rendering service to the Supreme Lord.
Ref >> Srila Prabhupada Vani.