Blessed are the poor in spirit...
For sin shall not have dominion over you: for you are not under the law, but under grace.
Grace is the key to a free, happy Christian life. There's two things that helps us live a victorious overcoming life and they are found in Romans 5:17:
For if by one man's offence death reigned by one; much more they which receive abundance of grace and of the gift of righteousness shall reign in life by one, Jesus Christ.
The Bible says our old man which was the engine of sin, died with Jesus when we believed (Rom 6:3-4). We are now like Jesus (1 John 4:17). Satan's biggest tool is we don't know who we are. So the first key to our being set free is learn as much as we can about God's grace which is what the gospel of the grace of Jesus Christ is all about. Romans is a great starting point and also listening to good, grace-based preaching and teaching.
The next key is becoming righteous conscious: that we are are righteous, not by our own efforts, but as a gift from God through Jesus Christ and therefore, there is NO CONDEMNATION.
The key to Paul's and our troubles in Romans Chapter Seven (count how many "I"'s are in that chapter - I count 36 "I"'s and "me"'s - it's what happens when we focus on self) is the very next verse of the next chapter: There is NO CONDEMNATION to believers (Rom 8:1).
Condemnation has been found to be THE root cause for defeat in a Christian's life. I know because freedom from condemnation in my own life (and many, many others) has changed me from a negative, defeated Christian to a strong, happy Christian. Condemnation runs deeper than fear and guilt.
Condemnation is Satan's only weapon that is formed against you and I. But what does Scripture say?
No weapon that is formed against you shall prosper; and every tongue that shall rise against you in judgment thou shalt condemn. This is the heritage of the servants of the Lord, and their righteousness is of me, saith the Lord. Isaiah 54:17.
So as Romans 5:17 says, when we immerse ourselves in the abundance of grace and the fact we are now and always will be the righteousness of God in Christ (2 Cor 5:21), we will reign in life, break Satan's power of condemnation, and all these things will be under our feet! Praise the Lord!