‘The final theme is one of pleasure and enjoyment. The word שִׂמְחָה (śim·ḥā(h)) occurs eight times in Ecclesiastes, and is always indicative of a cheerful emotion.  According to Qoheleth, God gave joy to men that were good in his sight.  He also stated, “God keeps him busy with the joy of his heart.”  Qoheleth celebrated enjoyment because unlike the other themes, it stemmed directly from worshipping God and seemed to remain with upright men through their entire lives.  He saw enjoyment as integral to having a good life on earth and commanded his people to do so. 
The theme of joy seems to be at the heart of Ecclesiastes. Qoheleth stated several times that God brought joy to those that were good and he kept them busy with the joys of their heart. Qoheleth observed that worshipping God properly brought joy into a person’s heart because God saw them as good. He also wanted his readers to serve the Lord and enjoy their lives even though the work they toiled for would not benefit them in the end because death eventually comes to all. Qoheleth told his readers, “nothing is better for them than to rejoice, and to do well in their lives, and also that every man should eat and drink and enjoy the good of all his labor—it is the gift of God.” Qoheleth also saw serving the Lord from an early age as instrumental to a joyful life. The concluding statement in Ecclesiastes sums the entire book up eloquently. The writer stated, “Fear God and keep His commandments, For this is man’s all. For God will bring every work into judgment, Including every secret thing, Whether good or evil.”
Unfortunately, many fail to grasp an accurate understanding of Ecclesiastes. Various scholars have emphasized a negative interpretation of the text which is often misleading. The Hebrew literature has many words that are similar, yet connote a range of nuances which are superficially translated in many English versions. Hě·ḇěl is often translated as “vanity” but from the above hě·ḇěl was demonstrated to have a much larger semantic range and can be rendered as “unknowable” or “incomprehensible.” If these translations were rendered into the English Bibles in the proper context much of the supposed pessimism would vanish.
It is reasonable to conclude that Qoheleth appreciated hard work, wisdom, justice, fear of God, and joy, and it was with these themes in mind in which he made judgments. Qoheleth saw these themes as essential to living the best life for God. He detested evil, unwise men that perverted justice and did not possess a reverence for God. These individuals made the lives of honorable people more difficult and often squandered the good works of others after their deaths. Qoheleth did not consider laborious effort vanity, but contended that men should enjoy their labor as he saw it was from the hand of God. Qoheleth asserted that God was a just God and would judge both the wicked and righteous in the end, and it was better to serve God through obedience than to offer the sacrifices of animals to cover one’s disobedience.  Joy was the main focus of Qoheleth; he told his audience several times to be joyful. The other themes in Ecclesiastes provide the backdrop in order for one to experience a joyful life. At the heart of the entire book, the author asked his audience to be content with their works, implement justice, and to fear the judgment of God to come; if his audience were to do these, they would have a meaningful and blissful life.’
Source: Shannon Byrd, “Ecclesiastes Explained: Unraveling the Negative Connotations” (unapologetic).
 James Swanson, Dictionary of Biblical Languages with Semantic Domains : Hebrew (Old Testament) (Oak Harbor: Logos Research Systems, Inc., 1997).
 The New King James Version (Nashville: Thomas Nelson, 1982), Ecclesiastes 2:26.
 Ibid., Ecclesiastes 5:20.
 Ibid., Ecclesiastes 8:15.
 Duane A. Garrett, Proverbs, Ecclesiastes, Song of Songs, vol. 14, The New American Commentary (Nashville: Broadman & Holman Publishers, 1993), 273.
 Ibid., Ec 2:9.
 Ibid., Ec 3:12-13.
 Ibid., Ec 11:9-12:1.
 Ibid., Ec 12:13–14.
 Ibid., Ec 5:1; 9:2.