God has given us the laws for our salvation. God gave us the law of Moses in the old testament and the law of Christ in the new testament. Then, what is God's will for giving us the laws? It is not the reason why God gives us the laws is not simply because He want us to keep it but because He want to fulfill 'love'.

According to Jesus' teachings all the laws in old testament can be compressed into two laws; "Love the Lord your God with all your heart and with all your soul and with all your mind" and "Love your neighbor as yourself". (Matthew 22:25~40)
For example, the ten commandments is the typical law in old testament given by God. It is divided into two commands; 'commands for God', 'commands for man'. Four commandments from the first to the forth are the commandments that we should keep in the relationship between God and us. And six commandments from the fifth to the tenth are that we should keep in the relationship between people. These two commands can be achieved with the aforementioned two laws: "Love your God" and "Love your neighbor"

Ro 13:8~10 Let do debt remain outstanding except the continuing debt to love one another, for he who loves his fellowman has fulfilled the law. The commandments, "Do not commit adultery," "Do not murder," "Do not steal," "Do not covet," and whatever other commandment there may be, are summed up in this one rule; "Love your neighbor as yourself." Love does no harm to its neighbor. Therefore love is the fulfillment of the laws.

Anyone who love another cannot do evil act which harms the love one. This is why the love is the fulfillment of the laws. In other words, all the commands for men can be fulfilled by the law "Love your neighbor as yourself."
Then, what about the commands for God? It is same. If we love God with our hearts, soul and mind we can never serve other gods or idols.

However, we can not achieve the love with the laws of Moses. So, in the new testament, God came in the flesh to save us, served us who are sinners and bore the sufferings on the cross. The laws that let us realize the love of God is the new covenant established by the sacrifice of God. When we keep the new covenant we can realize the love of God who sacrificed Himself shedding sacred blood. By realizing the love of God we become to love God with our hearts and minds. And also we can love our neighbors who God save with the love and sacrifice. The purpose that God gives us feasts of the new covenant, that is the law of Christ, is this. Therefore we should keep the feasts of new covenant and fully understand the love of God through the feasts. And should live a life that try to hard to achieve the love which is the fulfillment of laws.