If by the tongue you chant Hare Krishna mantra and by the tongue you taste prasadam, you will be perfect, simply by executing these two things.
The human body is rarely achieved and although temporary like other bodies, it is meaningful because in human life one can perform devotional service. Even a slight amount of sincere devotional service can give one complete perfection.
Working for Krishna is the ultimate perfection of all our activities.
One has to continue chanting the Hare Krishna mantra and preaching the chanting of this mantra because such preaching and chanting constitute the perfection of life.
Purport on Srimad Bhagavatam 4.24.67
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.
Regardless of time or place, one who chants the holy name, even while eating or sleeping, attains all perfection.