2 Peter 3:17

"Therefore, dear friends, since you already know this, be on your guard so that you may not be carried away by the error of lawless men and fall from your secure position." NIV translation

Since we know the truth, Peter urges us to hold on to it even in the face of the false prophets. Many have tried to use this verse to say that we can lose our salvation but, when he talks about "fall from your secure position", he is not talking about losing salvation. In Christ, our position as children of God is secure and God does not toss His children out on the street.

Peter is talking about those that have followed these false prophets into a religion instead of a relationship with Jesus Christ. Our position is sealed with the Holy Spirit and that Spirit will not allow you to be "carried away by the error" as He is the Counselor that Jesus promised.

2 Peter 3:18

"But grow in the grace and knowledge of our Lord and Savior Jesus Christ. To him be glory both now and forever! Amen." NIV translation

Peter ends this second letter by urging us to grow in our knowledge of Jesus and His grace. The more we learn about our faith the harder it is for us to be deceived by the schemes of the devil.