CS Lewis writes 

Food for thought 
How do Christians prepare for eternity? One of the problems that each believer faces is how difficult it is to conceptualize eternity—to see it for what it truly is. They attempt to measure it by time on earth; which

is a poor measuring stick. We can’t even fully grasp it, so knowing how to prepare for it seems impossible.

But the good news is that you don’t need to fully understand forever in order to prepare for a life in it.   

All Christ commanded each of us to do is to love God with all our heart, soul, and mind, and love others as ourselves. Granted, there are some details for how that is achieved, but the point is that all the instructions we need for eternal preparation have already been given.  All we need to do is devote our lives to following the instruction manual.