Do not present your members to sin as instruments for unrighteousness, but present yourselves to God as those who have been brought from death to life, and your members to God as instruments for righteousness. 

>By grace we have been justified, and therefore as a believer we are in Christ and must fully identify with Him. God sees the believer in the Lord Jesus Christ, no longer in Adam, but in Christ, the head of a new creation (Romans 6:1-7). But sin is still in our body, and will take control of a believer, if we let it. In this verse Paul is urging Christians to take control of our mind and body, and present our life to God for His good work.
If a believer obeys the old nature in its lusts, they will walk in the flesh and not in the Spirit. Whenever temptation comes, the believer must take refuge in prayer, in self-judgment and self-surrender (Paul says I die every day [to self] - 1 Corinthians 15:31) and give over his or her mind and body and flesh as instruments of righteousness for God. When we do this, we become useful in the church and our neighbourhood, building treasure in heaven.

See also Romans 12:1-2