Despite the dramatic rescue and amazing promise, sin happens in Noah and his family. Noah is not the hope of the human race, God is, because He will keep His covenant.
I am not the great hope of my life. Despite God's rescue and his ongoing promises to me, there is not going to be a future version of me that has managed to eradicate sin. Until I am made perfect with Jesus in eternity, any hope of growth in my life rests on His faithfulness.
When I become aware of sin in my life, I minimise it (assuming I can do better in that same situation next time) or am crushed by it (because I assumed I could do better this time). Both of those attitudes reflect a misplaced hope - in myself. Sin should cause me to run again to God in repentance, knowing that my only hope rests in Him.