Impartial God?

In our high school girls' small group, we have been studying 1 Peter. It has been very interesting and really good for both the girls and the leaders. In my reading, I came across this verse in 1 Peter 1:17:

17Since you call on a Father who judges each man's work impartially, live your lives as strangers here in reverent fear.

If God's heart's desire is for us to be with him for eternity, how can he impartially judge? This is another one of God's supernatural qualities that as a human I just can't fathom.