Ecclesiastes 5:17 says,  All his days also he eateth in darkness, and he hath much sorrow and wrath with his sickness. I believe that Solomon was saying that those who are living only for the things of this world would rather eat in darkness than to spend money to provide light to eat by.  Now we may see the very rich today spending a lot of money on themselves, but they still more often than not want to continue to accumulate more and more.  We can also interpret this as eating in spiritual darkness, because if the things of this world are all that matter, and a person has no time for God and His will, they truly are eating in spiritual darkness.  If a person like this becomes sick, that person becomes angry because they cannot gain more riches while sick.  They may also be angry because they realize that their life might soon be over and they will lose control of all they have worked for.  Verse eighteen says, Behold that which I have seen: it is good and comely for one to eat and to drink, and to enjoy the good of all his labour that he taketh under the sun all the days of his life, which God giveth him: for it is his portion.  I believe Solomon was saying that we are to enjoy the things God blesses us with.  We are not to starve ourselves or hoard what God blesses us with, but to use it under His guidance.  Too often we want our portion to be more than what God entrusts us with.  Verse nineteen says, Every man also to whom God hath given riches and wealth, and hath given him power to eat thereof, and to take his portion, and to rejoice in his labour; this is the gift of God.  If God does grant us riches, we are to eat, take our portion, and rejoice in our labor.  This does not say that our portion is increased and that we are to rejoice in our riches.  God does not bless us with riches to flaunt them, but to help others.  Verse twenty concludes the chapter with, For he shall not much remember the days of his life; because God answereth him in the joy of his heart.  If we are living for God, we will live with joy in our heart.  We will not much remember the work or the rewards, but our joy will be from serving God.