The futility of us... the centrality of Him.
In fact, there are only two things Solomon appears to know for sure. First, try not to die. For whatever reason, it seems dying is not a good thing to Solomon. Second, God reigns!
Through this entire section, the one unchangeable, unshakable, unaffected, righteous, and generous character that we see is God. Take some time, if you can, and read these three chapters, focusing particularly on the lines that reference God. Notice the reverence that is given Him that Solomon does not even give other royals like himself. No matter what we see in this fallen world, we must continue "holding on to faith and a good conscience" (1 Tim. 1:19) saying "God be praised" in all circumstances.