Nothing, except we are born with a sinful nature, the old Adam that lives in all of us, except Jesus, and will have it until we die. But thanks be to Jesus Christ, we who are in Christ Jesus and He in us are no longer slaves to that sinful nature. We no longer want to live a life controlled by sin, but controlled by the indwelling HS.
Now, the old Adam can rear its ugly head sometimes, due to stress, illness, fatigue, etc. But "if we confess our sins, God Who is faithful and just will forgive us our sins, and cleanse us from all unrighteousness." We admit our sin, and lay it at the foot of the cross of Christ, pleading for forgiveness, and receive it.
This isn't that difficult to comprehend, pilgrim.