Life in Christ...

"There is therefore now no condemnation for those who are in Christ Jesus." (Romans 8:1)
 Why?
Because: "...You have died to the Law through the body of Christ..." (Romans 7:4)
..."   Wretched man that I am! Who will deliver me from this body of death? Thanks be to God through Jesus Christ our Lord! So then, I myself serve the law of God with my mind, but with my flesh I serve the law of sin." (Romans 7:24-25)
I can't do it on my own! That's reality!
"For the law of the Spirit of life has set you free in Christ Jesus from the law of sin and death. For God has done what the law, weakened by the flesh, could not do. By sending his own Son in the likeness of sinful flesh and for sin, he condemned sin in the flesh, in order that the righteous requirement of the law might be fulfilled in us, who walk not according to the flesh but according to the Spirit."  (Romans 8:2-4)

"The righteous requirement of the law is fulfilled in us..." (vs. 4)
What does that mean?
Let me give you this illustration: Internet law, if you will, requires a server. You want a web site, you need a server. In order for a website to be their at all times, the server must remain on at all times. However, I can post on my google blog (as I'm doing right now), turn my computer off, and walk away; and yet my post will remain online for others to view at their leisure even though my computer is off, and I'm in deepest darkest Africa. That is because the requirement of internet law (a server) was fulfilled by someone else (Google). I published my blog post on their server. In essence the requirement of internet law was fulfilled in me, since the post has my name on it, even though Google did the law fulfilling.
See, what happens is that God through Christ fills up what the law requires in us, as we walk by the Spirit.