Pure devotional service is the satisfying activity for the soul. So Lord Caitanya was specifically preaching pure devotional service, this was his unique contribution. Even in the history of whole vedic culture it was very rare to find someone who is preaching pure devotional service, other than Narada-muni and some acharyas. Lord Caitanya was very strict he wanted his followers to maintain that integrity of preaching only pure devotional service. When some of his followers visit other people who are not preaching pure devotional service, he would abandon them.
Remembrance of Krishna is not possible for the impure soul who has not practiced Krishna consciousness in devotional service. Therefore, one should practice Krishna consciousness from the very beginning of life. If one wants to achieve success at the end of his life, the process of remembering Krishna is essential. Therefore, one should constantly and incessantly chant the Hare Krishna Maha Mantra.
By performing congregational chanting of Hare Krishna mantra, one can destroy the sinful condition of material existence, purify the unclean heart and awaken all varieties of devotional service.
Everything that can be achieved by fruitive activities, penance, knowledge, detachment, mystic yoga, charity, religious duties and all other means of perfecting life is easily achieved by My devotee through loving service unto Me. If somehow or other My devotee desires promotion to heaven, liberation, or residence in My abode, he easily achieves such benedictions.
The wild tigers, elephants, bear and deer all together accompanied the Lord, and the Lord accompanied them in sankirtana. By this He proved that by the propagation of the sankirtana movement (congregational chanting and glorifying of the name of the Lord) even the wild animals can live in peace and friendship, and what to speak of men who are supposed to be civilized.
Srimad Bhagavatam Introduction.
Men become strong and stout by eating sufficient grains, but the devotee who simply eats ordinary grains but does not taste the transcendental pastimes of Lord Chaitanya Mahaprabhu and Krishna gradually becomes weak and falls down from the transcendental position.
Animalistic envy exists in human society as long as there is no performance of sankirtana-yajna.
Purport on Srimad Bhagavatam on 4.30.35
Those who are meek and humble, which most of the people are not, can enter into the kingdom of God.
Always there will be doubts. Always there will be disturbance. Always there will be injustice. Among all these, tolerate & co-operate.
All kinds of activities, both auspicious and inauspicious, that are detrimental to the discharge of transcendental loving service to Lord Sri Kishna are actions of the darkness of ignorance.