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.
If the devotee feels that, "I can be Krishna Conscious without the association of devotees." it is very dangerous situation. More we separate from devotees, more we bounded by the attacks of Maya. The material world is designed to struggle to exist. So, Srila Prabhupada made the situation minimum by having Krishna conscious temples, communities and farm projects, so devotees can live in association with devotees.
Mind is seat of senses, to control mind is very important aspect. We need to understand our duty to train our mind. We need to discriminate and we need to chastise the mind sometimes, we need to distinguish what is bhakti and maya.
Even in the books of patanjali yoga, it is said that in order to attain perfection in yoga one needs Hari-bhakti. Ultimately devotion is the perfection. Narayana Smriti at the end of one's life is perfection. Normally people end their life thinking of whatever their attached to. If we are chanting the Lord's names and engage in his service then we maintain an attachment for the Lord throughout our life. The Lord will be the common denominator and pivot point in our different activities. Whatever process one is engaging in, this remembrance of Narayana, taking shelter of the Lord is the most important aspect.