Jesus emphasized that He came not to abolish the Law, but to fulfil it. He used the word "fulfil", not "keep". It is Jesus who fulfills the Law. And we, who are more and more in him, and He in us do what He does.
Jesus said: "everyone who looks at a woman with lust has already committed adultery with her in his heart". Jesus asked us to simply avoid illicit sexual union, but to be chaste in all matters and in mind and heart. What the Lord is offering us here is a clean mind and pure heart.
Jesus said if our eye or our hand causes us to sin, it is better to have it cut off and thrown away. In this age, we make light of sin, especially sexual sin. Jesus used hyperbole to warn us: it is better to lose our eyesight and our limb than to sin!
In Jesus' time, divorce was permitted in Israel, but a man had to follow the rules. But Jesus said that to fulfill marriage law is to love our spouse. When Jesus lives within us, love for our spouse will grow, love for our children will deepen. It would be impossible to think about divorce.
Let us be transformed by God! We can only be authentic Christians with Jesus living His life in us.