Wow, what a good question! :)
What did Jesus say? Matt 22:37 "You shall love the LORD your God with all your heart, with all your soul and with all your mind" and Matt 22:39 "You shall love your neighbor as yourself". Or maybe what the Apostle John wrote in I John 4:8 "He who does not love does not know God, for God is love". Why did Jesus die on the cross for us? John 3:16 " For God so loved the world that he sent his only begotten Son, so that whoever believes on him should not perish but have eternal life". So, what is our part? Love God and love others. The parable of the Good Samaritan shows us that everyone is our neighbor. If we live our lives truly loving God and loving others, then we will have lived as Christ wants us to live. John 17:21-23 sums it up rather nicely: "That they all may be one, as You, Father, are in Me, and I in You; that they also may be one in Us, that the world may believe that You sent Me. And the glory which You gave Me I have given to them, that they may be one just as We are one: I in them, and You in Me; that they may be made perfect in one, and that the world may know that You have sent Me, and have loved them as You have loved Me." So, we should be sharing the Father's love for us with others.