The Preacher not only observes difficult things in life. He is not just gloomy. He also sees good things: things that can truly be enjoyed and give pleasure.
It is good to enjoy life; to eat and drink well; to enjoy the many beautiful things in life. It really is not a sin to enjoy some rest after a hard day's work. The Preacher says that it is good and fitting when you are able to enjoy your life like this.
17 Voici ce que j'ai vu: c'est pour l'homme une chose bonne et belle de manger et de boire, et de jouir du bien-être au milieu de tout le travail qu'il fait sous le soleil, pendant le nombre des jours de vie que Dieu lui a donnés; car c'est là sa part.