Here the teacher is telling us that we can strive all we want but unless our striving is done under the direction of God then our striving will leave you feeling as empty as all the verses that came before this. Yet look around for the good things that God has gifted to you and enjoy them. If you cannot or will not see them as gift then they can never be enjoyed the way that God intended them to be. The teacher here even goes so far as to say that the understanding of good things being from God is a gift and those who do not understand have refused to received a gift from God.