In spite of his painful encounters with the world and its problems, Solomon does not recommend either pessimism or cynicism. Rather, he admonishes us to be realistic about life, accept God's gifts and enjoy them. He advises us to trust God and enjoy what we do have rather than complain about what we don't have.
Warren W. Wiersbe, Be Satisfied (Ecclesiastes): Looking for the Answer to the Meaning of Life
complaining, gratitude, worship