Philippians 1:27 (NKJV)
It has been said that if you climb a mountain from one side you have one view, but if you climb a mountain from the other side you will have a completely different view. Also, two people can tell a story from two different perspectives and while they are talking about the same thing they might emphasize different aspects of that same story. Someone who has only seen one side of a mountain or knows just one part of a story may say that they have the correct view. But, neither side of the mountain or story is the right or wrong side necessarily, but to have a complete understanding of the mountain or story you usually need both sides.
If you ask Christians what the Gospel is, many would talk about how Jesus came from heaven to take our place and die on the cross for our sin. Some would say that the Gospel is good news and that through Christ we have been made right with God. Others would talk about how Jesus came to give us an abundant life or about our future hope of being with God for eternity and not going to hell. All of these things are true, but they mainly focus on one side of the story, the aspect of our benefits because of the Gospel. The Gospel is indeed good news for man, but it is also much more.
We often look at the benefits we have received from God through Jesus, and there are benefits, but we fail to see the responsibilities we have also been given. As Paul mentioned to the Philippians, we have a responsibility to live in a way that pleases God and promotes the Gospel. We are not just told to go and live a happy life of our own making, we see that God has a plan and a purpose for our lives and we must focus on fulfilling that: being a good representative of Jesus Christ, walking in love, spreading the Gospel around the world, and living a life worthy of the One who saved us. Get both sides of the Gospel and you will have a complete picture of what it means to be a Christian.