The Purpose of the Law..and the Promise

I am on my second read-through of Galatians and finally understanding the purpose of the law..I have had a hard time justifying the God of the Old Testament with the God that Jesus teaches us about in the Gospels..but now I feel like I am starting to grasp it..the PROMISE of God received by FAITH was given to Abraham - in you all the nations of the earth will be blessed - ..the law 400 something years later was an addendum, given by God, to get it through our minds that no matter how hard we tried, we could not reach right relationship with God through rule-keeping..Christ was the promise and through Him taking our curse, we now have direct access to God through our faith in the sacrifice of Jesus..we are made righteous before God because of Jesus!!!