1 Peter 4:1

"Therefore, since Christ suffered in his body, arm yourselves also with the same attitude, because he who has suffered in his body is done with sin." NIV translation

"Therefore" refers us back to verse 18 of chapter 3 and it reminds us that Jesus died for our sins physically but makes us alive by the Spirit. Peter is telling us that, since we were saved from sin and are made alive by the Spirit, our minds should also be transformed to seek the will of God. We are released from sin and God has provided a way for us to live the Christian life (walk the talk). The way to live the Christian life is to turn our minds over to God and the direction of the Holy Spirit. We are done with sin; we do not belong in sinful situations; we cannot be comfortable in them and if we listen to the direction of the Spirit, God will lead us out of those situations. If we are comfortable in sin, we need to check our relationship with Jesus Christ.

1 Peter 4:2

"As a result, he does not live the rest of his earthly life for evil human desires, but rather for the will of God." NIV translation

Jesus did not purchase us on the "lay-away plan" He purchased us for the here and now as well as for eternity. Since we are His now and the focus of our minds has been changed, we do not live to satisfy ourselves. Our transformed minds are focused on serving God and doing His will. How do we know His will? We are told, in Ephesians 2:10, that God prepared things for us to do, as Christians, even before we came to be Christians. Listening to the Spirit and watching for these things is a large part of the will of God for the life of a believer.