There is a God who made us. This God knows us and loves us. He desires to have a relationship with us. Dying on the cross, God's son Jesus Christ atoned for all of our sin and now invites us into his family. God wants us to know him as a father, and Jesus as a brother. The Bible speaks of people who talked to God as one talks to a friend, and that is the sort of friendship which we can have with God.
This means that being a Christian isn't about keeping a bunch of rules - it's about a relationship. The Christian life is one of knowing God and being known by God. It is one in which we are absolutely, unconditionally, permanently accepted by God because of the work of Jesus. We don't have to put up a front or get our life right for God to accept us. We just have to come to him in faith.
God did not abandon this world to its brokenness, but through the person of Jesus Christ entered in to bring us hope, healing, restoration, forgiveness, and eternal life. The Bible says that "the creation itself will be liberated from its bondage to decay and brought into the glorious freedom of the children of God." God sent Jesus so that "through [Jesus] all things will be reconciled to God, whether things on earth or things in heaven, because he made peace through his blood, shed on the cross." We have hope that though in this world we face darkness, disease, evil, and especially the consequences of our own daily shortcomings, one day we will all be set free from this. God will restore both us and the earth to its intended glory.
When you experience a relationship with Jesus and grab hold of this eternal hope, you want to give back. We can never repay God, but we can live for him day in and day out. Knowing Jesus will shift our focus from ourselves to God and others. We can be set free from feeding the bottomless pit of our ego with money, reputation, power, experiences, and luxury. Instead, we can become blissfully self-forgetful and live for the good of others, receiving the greater joy that comes from a life of purpose beyond yourself.