Sree Sree Guru Gaurangau Jayatah!
The root cause of our being imprisoned in the prison-house of worldly bondage is our aversion to Supreme Lord. After forgetting Sri Krishna—The Supreme Lord, and being enveloped by the illusory energy, we passed through eight million births as aquatic animals, trees, worms, birds and beasts and after that we got this precious human birth. God has bestowed discriminating power to human beings between eternal and non-eternal, so that they are capable of accepting Eternal Truth by giving up non-eternal things. This human birth is not meant for eating, sleeping, defending and mating like beasts and birds. Human beings can worship Krishna (God). But any moment we may lose this chance.
We have imbibed bad and good thoughts in our minds by passing through so many births. So it will take time to remove the bad thoughts and enhance devotional eternal good thoughts. Supreme Lord Sri Krishna has advised in the Gita that through `Abhyasa yoga’— spiritual practice of subduing the evil thoughts and enhancing good eternal thoughts— by sincerely practising, gradually we will be able to get stable state of mind.
— Srila Bhakti Ballabh Tirtha Goswami Maharaj