On repeated sinning

What does the bible have to say on someone who sins repeatedly? Will he still be valid for salvation? Does God consider the motives of the man in his sinning? I have considered the following 2 verses in the bible during my contemplation.

1 John 3:6-10: No one who lives in him keeps on sinning. No one who continues to sin has either seen him or known him. Dear children, do not let anyone lead you astray. He who does what is right is righteous, just as he is righteous. He who does what is sinful is of the devil, because the devil has been sinning form the beginning. The reason the Son of God appeared was to destroy the devil’s work. No one who is born of God will continue to sin, because God’s seed remains in him; he cannot go on sinning, because he has been born of God. This is how we know who the children of God are and who the children of the devil are. Anyone who does not do what is right is not a child of God;

Based on this verse, how should one view a Christian who sins after he has received the faith? Will that Christian not be amountable to condemnation as being from the devil if based on this verse? Well, there are good grounds to condemn one as being from devil, especially when the sins committed are intentional and calculated. This includes the likes of scheming and plotting the use of underhanded means to attain one’s objectives. But what about the sins of the passions? It's lust for men, and probably envy for women.

Then, I considered the following verse below

Romans 7:15-20 :I do not understand what I do. For what I want to do I do not do, but what I hate I do. And if I do what I do not want to do, I agree that the law is good. As it is, it is no longer I myself who do it, but it is sin living in me. I know that nothing good lives in me, that is, in my sinful nature. For I have the desire to do what is good, but I cannot carry it out. For what I do is not the good I want to do; no, the evil I do not want to do—this I keep on doing. Now if I do what I do not want to do, it is no longer I who do it, but it is sin living in me that does it.

This verse seems to acknowledge the possibility of a Christian to sin. However, the sin committed is in conflict with his desires to lead a life congruent to Christian principles. Is there a way to reconcile the two seemingly contradictory verses? The distinction that I would draw is that the kind of sin described in 1 John 3:6-10 is in the deliberate form whereby one chooses to commit the sinful action, whilst Romans 7:15-2 is about sins of the passion, whereby one sins despite his wish not to do so because of his predisposition to be waylaid by temptation.