Ecclesiastes 3:13 says, And also that every man should eat and drink, and enjoy the good of all his labour, it is the gift of God.  Solomon may have felt that everything done in this world was vanity, but he still felt that we should enjoy the fruits of our labor, since it was a gift of God.  It is when we begin to feel that we are doing everything on our own instead of everything being a blessing from God that we begin to have problems.  We start to look to the things of the world to bring satisfaction and feel that everything God blesses us with is our to use as we see fit.  This was never God's intention.  He blesses us so that we may do His work and help others.  Verse fourteen says, I know that, whatsoever God doeth, it shall be for ever: nothing can be put to it, nor any thing taken from it: and God doeth it, that men should fear before him.  Solomon said the things of God are everlasting.  God created everything for a purpose, and the purpose of mankind is to love God above all else.  God gave us free will, so we may choose the things of this world over the will of God for our lives, but it does not change our true purpose.  The things we do for God last forever, and the things we do for material reasons will pass away.  The question then becomes which do we put the most emphasis on.  If all our time and energy are spent gaining and maintaining the things of this world, we, like Solomon, are going to see the futility of it all.  We must put our effort into the things of God.  His purpose for us is never going to change, no matter how much or how little we are blessed with in this world.  Then verse fifteen says, That which hath been is now; and that which is to be hath already been; and God requireth that which is past.  When we feel that the world has gotten so much worse or so much better than in the past, God says it is as it always has been.  We can only come to God in faith through Christ, and our past can neither save us or prevent our being saved.  As Solomon said earlier, there truly is nothing new under the sun.  God is never taken by surprise by the actions of humanity.