At first glance, I considered splitting this verse in half and making it two entries. The first would emphasize that we cease to sin when born of God, and the second would focus on His protection over us. Upon further meditation, however, I realize it is a complete thought and impossible to bisect. We, children of the Most High, do not continue sinning, not of our own accord, but strictly because He bars the evil one from having affect. This influence holds no power over us when we come into the fold of our Good Shepherd. I read the Psalms, in light of this, and am amazed at the language used to convey the Lord's safeguard of us. The poets speak of a mighty King, strong and righteous, on His throne and ever-watchful over His children. They sing of running to Him for shelter and security, healing and rest. Brothers and sisters, this is our Lord and we are safe in His great arms!
But then, why do we continue to sin? It says here, pretty clearly, that we shouldn't and yet we do! How does that work? There is still a battle within ourselves – the enemy no longer has a hold on us, yet we still have the freedom to choose his way. It is in Christ that we find strength to make the right choice, and confidence of that in the affirmation of the Spirit. The Lord protects us, keeps us from stumbling (as Jude points out in his letter to the Church), and our part is to dwell in that protection, to abide in Christ because without Him we will fall.