"God did not create a meaningless world." (ACIM Workbook Lesson 14)
This lesson teaches us about what is real and what is not real. We learn this by making the distinction between what has been eternally created and what has been temporarily made by us.
What has been made by us by thought and concept is dependent on conditions. Thus it cannot be real in an eternal sense, and is only a phantom. Conversely what God created is changeless and has always been.
Once we sort the real from the unreal, we need only concentrate and focus our attention on the real! The unreal will then lose its importance in life and fade into the dream that it always was. The real remains "shining", our foundation, and self-evident as it always has been.