All mans efforts are for his mouth, yet his appetite is never satisfied. (v7)
Our can hunger instruct us. We are creatures, finite beings with needs (like food). God is uncreated, infinite and without needs.
Despite my continued efforts to feed myself, I am often hungry again within hours. It is an endless pursuit. This cycle can be used to remind me of my dependence on a God who is not like me. That helps me with humilty.
However, when my focus has shifted, the constant repetition of life feels tiresome and unending. I think this is where Solomon is when he's penned these words, he's lost sight of his great Provider.