according to Vaishnava theology:
Human life is a chance for us to turn back towards God. We are His seperated parts and parcels. Some choose to live with God eternally, others think hey "let me be independent" and voila - the material universe is created for us to all play at being so. Once we fully change our mind (or more correctly our "heart") we can go back into the eternal garden.
God's a fair person so He sends people to canvass on His behalf, or sometimes communicates Himself directly. What is said varies according to time & circumstance and who is hearing the message, but essentially the advice is being said for the same purpose.
Time rolls on...
... Neemai