Krishna allegorically represents the spirit, soul atman existing in our heart. It realizes its full potential when human beings indulging in spirituality reached state of enlightenment.
State of enlightenment means the real inner self of us, our soul atman reaching state of absolute purity. Indulging in spirituality when human beings negate karma to zero, in absence of dross impurities within the soul atman finally gains absolute purity forever.
In the state of absolute purity, Krishna is equated with Vishnu. Every enlightened soul like Mahavira, Gautama Buddha even Jesus Christ and Prophet Mohammed experienced stages of both Krishna and Vishnu in their life.
And what does Vishnu denote? Lying on a bed made by Shesha (the multi-hooded serpent King) Vishnu is always represented with Lakshmi sitting at her side. Allegorically this means state of enlightenment is reached demolishing ego in totality, establishing total control over desires and wishes, five senses and mind.
Control over earthly pleasures is represented by Lakshmi sitting by side of Vishnu.
Sri Ramakrishna Paramhansa and Maharshi Ramana after reaching state of enlightenment experienced stages of Vishnu many times. Both Sri Ramakrishna Paramhansa and Maharshi Ramana finally succeeded in becoming a Krishna and finally Vishnu in their lifetime.
The character of Vishnu in spirituality depicts a liberated soul atman that could venture to any part of cosmos at will. The Shesha is always shown, existing in Bhav-sagar. The Shesha represents a fully awakened kundalini shakti, the dormant lying serpent energy in base of spine. And Bhav-sagar represents the entire cosmos.
Even now in present times all liberated souls like Mahavira, Gautama Buddha Jesus Christ, Prophet Mohammed even Adi Shankaracharya, Sri Ramakrishna Paramhansa and Maharshi Ramana existed in Bhav-sagar and these energies can be invoked by anyone on mother earth for their blessings.
As per Bhagavad Gita ultimate goal of human life is indulging in spirituality never religion (rituals), the path taken by all enlightened souls that manifest mankind.