Ecclesiastes 2:21 says, For there is a man whose labour is in wisdom, and in knowledge, and in equity; yet to a man that hath not laboured therein shall he leave it for his portion. This also is vanity and a great evil.  Solomon said that those who lived and worked wisely would eventually leave what they had attained to someone who had not worked for it.  He saw this not only as vanity, but as a great evil.  Of course he knew he couldn't take the things of this world into the next, but he felt it was evil to leave everything to someone who could waste it all away.  If Solomon had been using his wisdom and wealth to benefit his subjects, those he was to be a righteous king over, he might not have had this problem.  He could have seen what his labor accomplished and not have had to be upset that he would have worked to leave everything to another.  Solomon was still focused on himself and not on what God had done for Him.  When we begin to feel that everything that we have gained in life is due to us, it can become a source more of stress than joy.  We wonder how we can keep it and control it.  If material blessings are seen to be from God and are put under His control, this will not be the case.  Verse twenty two says, For what hath man of all his labour, and of the vexation of his heart, wherein he hath laboured under the sun?  As Solomon continued to look back on his life, he saw little of value in it.  If we live our lives only to amass the things of this world, ultimately we are going to look back the same way.  As followers of Christ, we are called to do everything for the advancement of His kingdom, not to look at all the blessings of life as being for our own purpose.  Verse twenty three states, For all his days are sorrows, and his travail grief; yea, his heart taketh not rest in the night. This is also vanity.  I believe  Solomon was saying that when our total focus is on gaining and keeping the wealth of the world, there is never any rest.  We end up working by day to gain it and worrying at night how to keep it, and it all passes to someone else when we die.  That is indeed vanity, or nothingness.