What is the first and greatest commandment?
36 Master, which is the great commandment in the law?
37 Jesus said unto him, Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind.
38 This is the first and great commandment.
39 And the second is like unto it, Thou shalt love thy neighbour as thyself.
That is why it is said in the Bible, how can we love God if we love not our brother. Read what Jesus said about His first and second commandment again.
If you look at the 10 commandments in the law, the 1st and 2nd commandment that Jesus talked about encapsulates the spirit of the 10 commandments. Read it again. [Exodus 20]
Jesus loved us while we were yet sinners, when we understand the revelation of that grace, we will learn, through His grace, to love even those who are difficult to love. Sometimes, God puts us in that situation for us to learn ... our whole life is a school of learning about God and His grace.
When we love God above all else, and love our brothers/sisters as ourselves, we will fulfill many things in the law ... not to kill, not to covet someone else's wife, not to steal etc. So, you can see that God's wisdom is all encompassing. In two commandments, Jesus has shown us how to live.
If we try to live by the law with our own works, we will fail, but if we live and depend on His grace, God will help us to mature and to be more and more like Him. Hope this helps.