Jesus told us the greatest commandments are to love the Lord our God with all our heart sold and mind and to love our neighbor as our selves (Mathew 22:37-38). If we have a bad habit of looking on the dark side like the author of Ecclesiastes, we will focus on our failure to do this.
However, God does not give commandments to frustrate us but to bring blessing. We help each other when we fall. We keep each other encouraged. We support each other in struggles. We give each other strength (Ecclesiastes 4:9-12).
Our lives are enriched when we love each other with the same intensity with which love ourselves.