What is the root cause of my sin?

I was watching this video about iniquity and decided to share it with you. 

Important Scriptures

• I will cleanse them from all their iniquity by which they have sinned against Me, and I will pardon all their iniquities by which they have sinned and by which they have transgressed against Me (Jeremiah 33:8, NKJV).
• But He was wounded for our transgressions, He was bruised for our iniquities; The chastisement for our peace was upon Him, and by His stripes we are healed (Isaiah 53:5, NKJV).
  
• If I regard iniquity in my heart, the Lord will not hear (Psalm 66:18, NKJV).
• If we confess our sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness (1 John 1:9, NKJV).