We must be careful to walk a fine line in our journey. On one side of the line is looking at Christianity as something that solves all of our problems and where only happiness should be found. On the other side, if you talk about evil and sin too much you could end up glorifying it. So we must walk the middle and have a healthy view of evil and good and how all of that works within the kingdom.
We cannot truly appreciate our salvation, the goodness of God, the sacrifice of Christ, unless we have a healthy respect and understanding of sin and evil within our world. It is never a "fun" Sunday to take time to lament or confess or even recognize the brokenness of our world. However, if we only have fun on Sunday then we miss the point of why we point to Christ. Why do we point to Christ? We may answer that our lives are better off with Jesus. We may answer that worshipping God gives us a good feelings. We may answer that without Sunday we cannot make it through the rest of the week. All of the answers are more about us than Christ. We point to Christ, because in the cosmic war of good versus evil or angels vs. demons or Christ vs. Satan, Jesus Christ sacrifices his divine nature to live in this world, and then later sacrifices pain, anguish, and ultimately sacrifices his life so that we can have a perfect, ultimate conqueror to follow. When Jesus overcomes evil, so do we!