One of the themes in 2 Peter is the need for believers to be ready for Christ's return, a day that will come like a thief (3:10). Peter (along with the rest of the New Testament) does not teach that you will be saved for sure just because you followed Christ in the past. Quite the contrary. You who are believers need to "make every effort to confirm your calling and election" (1:10).
And Peter is not addressing nominal believers here. He is addressing believers who have a "secure position" (3:17). He doesn't want them to stumble (1:10) and fall from it (3:17). It is the same prayer for believers that we will see soon in Jude 24, where Jude prays to the God who is able to "keep you from stumbling."
Peter clearly doesn't know anything about the many debates theologians will later have about salvation being by faith and not by works. Peter says it takes effort (1:10). Peter doesn't know anything about eternal security for someone who has been saved--you can fall from a secure position (3:17). He knows nothing about election being unconditional--you have to work to confirm it (1:10).
The way some Christian traditions talk about "election" and "calling" makes me think of a line from a famous movie, "You keep using that word. I don't think it means what you think it means."  As I said about grace language in the chapter on 1 Peter, grace came with expectations. True, one could not earn grace. True, the gift was always disproportionate to the response. But God's gift of salvation expects us to follow him to the end. If we are not following him when he returns, then we simply will not be saved... 
 The Princess Bride (1987).
 A Calvinist might say that Peter is speaking informally here when he talks of election, that he is speaking to all those who appear to be elect and chosen. Among those who appear to be Christians, they might say, some are truly elect and others only appear to be elect. In this view, only those who are truly elect will make it to the end. The interesting thing about this approach, though, is that it requires us to say that the way the word "election" is used in 1 Peter is not the true definition of election.