What is devotional service or the worship of the Lord?

Whatever is done for Krsna’s pleasure is devotional service. Rendering service to the Lord is called devotional service. Dasya-rasa, sakhya-rasa, vatsalya-rasa, and madhurya-rasa are each progressively superior. Favorable cultivation of Krsna consciousness without any tinge of anyabhilasa, karma, jyana, yoga, tapa, or vrata is called bhajan, worship of the Lord. Nondevotional processes such as hatha-yoga, raja-yoga, karma-yoga, jyana-yoga and vrata-tapasya-yoga cannnot be called bhajan. It is not possible to purify the heart completely by practicing karma, jyana, yoga, tapa, or vrata. Only devotional service or hearing hari-katha can purify the heart completely. Even the restless mind becomes purified and pacified simply by serving the Supreme Lord.