Again, from introduction to Ecclesiastes in the NIV Study Bible.
1. Accept the human state as it is shaped by God's appointments and enjoy the life you have been given as fully as you can.
This is hard for me. I always want to change things that are screwy or counterproductive. (BETP Master Guidelines, for example.) But I can't change the nature of bureaucrats any more than I can change the nature of bees. Bees make honey, bureaucrats make rules. I can adapt, I can move on, but above all I need to remember that when Jesus showed up in the flesh, he didn't spend time trying to change the laws and rules and regulations. He worked on hearts and souls and frail human flesh. So it's important to keep that perspective -- that the rules will come and go, but the souls of the bureaucrats, like the souls of the people toiling under the rules, will last forever.
2. Don't trouble yourself with unrealistic goals -- know the measure of human capabilities.
But note that it's unrealistic goals one is to avoid. ("God grant me the serenity to accept the things I can not change....") One must seek God's wisdom, not man's wisdom, to identify appropriate goals. William Wilberforce, after all, took on the goal of abolishing slavery -- quite a mouthful to bite off! Vivien Thomas took on the goal of making heart surgery a reality. So clearly this isn't a caution not to set big goals. But all things considered, it's the eternal perspective one needs to keep, and allowing God to appoint times and places and people.
3. Be prudent in all your ways -- follow wisdom's leading.
Imprudence just gets you and others hurt.
4. "Fear God and keep His commandments."
And trust Him to order things as they need to be. Esther's parents didn't do anything at all that was worth recording in the Bible -- but had they not married and had a child, what would have happened to the Jews? But it was Esther who came into the world "for such a time as this."
To sum up, Ecclesiastes provides instruction on how to live meaningfully, purposefully and joyfully in the theocratic arrangement -- primarily by placing God at the center of one's life, work, and activities. In contentedly accepting one's divinely appointed lot in life, and by reverently trusting in and obeying the Creator-King.