Romans 6:12, 13 - Being A Christian Is A Matter Of Life Or Death; part 1

Romans 6:12, 13 (NIV) Therefore do not let sin reign in your 
mortal body so that you obey its evil desires.  Do not offer the parts 
of your body to sin, as instruments of wickedness, but rather offer 
yourselves to God, as those who have been brought from death to life; and 
offer the parts of your body to him as instruments of righteousness. 

Romans 6 is about "present tense" salvation. We are being saved 
by Christ as He releases us from the grip of sin and enables us to 
live a righteous life now. [Victor Bible Reader's Companion] 

Count yourselves dead to sin means that we should regard our old 
sinful nature as dead and unresponsive to sin. Because of our union and 
identification with Christ, we are no longer obligated to follow through with 
those old motives, desires, and goals. So let us consider ourselves to 
be what God has, in fact, made us. We have a new start, and the 
Holy Spirit will help us become what Christ has declared us to be. 
(Life Application Commentary) 

The charge to count oneself dead to sin but alive to God in 
Christ Jesus is in the present tense, indicating a necessity to keep up 
the process if one is to avoid reactivating the body of sin. 
Paradoxically, the Christian is dead and alive at the same time, as in 
Galatians 2:20, dead to sin and self but alive and responsive to God. He 
is to give no more response to sin than a dead man can give. On the 
other hand, all the potential that redeemed life affords is to be 
channeled Godward... this process must not be undertaken in a mechanical 
fashion, as though there were some sort of magic in going through the 
motions. One must really desire to have freedom from sin and to live 
responsibly to God. To that end he must avail himself of the means of grace, 
particularly the diligent use of Scripture and faithfulness in prayer. 
[Expositors Bible Commentary re vv. 11-14] 

For the purpose of explaining the Christian experience, Paul 
speaks of a believer as if he consisted of two selves. The old self is 
now dead, for it has been crucified with Christ (v. 6). The new self 
is alive, born again of the Holy Spirit (v. 4). Thus Paul can speak 
of a man as being at the same time dead in relation to sin and 
alive in relation to God. In addition to this, Paul seems to set a 
man's consciousness apart from the old and new selves, so that the 
believer is able to decide consciously with reference to keeping the old 
self dead and the new self alive. [SDA Commentary] 

Though our "old man" is described as crucified with Christ (v. 
6), we are still in our "mortal body," with its earthly desires and 
cravings. Sin is still a power. If we so allow, sin may still have 
dominion over us. Being born again of the Holy Spirit does not eradicate 
the earthy desires of the flesh. However, the experience places us 
in touch with a higher power by which we may ever successfully 
resist the attempted domination of sin. But it still rests with us to 
decide whether we will give our continued allegiance to sin or to 
Christ.  It is for this reason that we must experience a "fresh 
conversion" every day (see 1T 699; 7T 44). Our experience of yesterday is 
not sufficient for today. Though we may have died to sin yesterday, 
our "old man" may rear his ugly head again today. Only by keeping 
our old selves continually and completely dead to sin, as 
represented by our baptism, are we able to live daily unto God. And this 
experience is possible only through union with Jesus Christ, by a faith in 
Him that is so real and so constant that like Him we hate sin and 
love righteousness. [SDA Commentary] 

When a person is determined to do something or to hold a certain 
belief or idea, we say that person has a certain mind-set.... Paul 
indicates that all mind-sets can be reduced to two categories: sinful and 
spiritual. The two mind-sets are not parts of a person or even forces 
within a person. They signify powers and dominant features of two 
realms, the spirit and the flesh (former sinful nature). 
The sinful mind-set 
Consciously and unconsciously life will be oriented toward: 
Hostility toward God 
Resistance to any form of submission 
Actions and attitudes that will not please God 
The spiritual mind-set 
Consciously and unconsciously life will be oriented toward: 
Life and peace 
Friendship with God 
Obedience to the Spirit's influence 
Guidance by the Holy Spirit 
Love for God and neighbor 
Knowing and following the words of Jesus 
(Life Application Commentary Series)