Customarily we would define vanity as an over-attention to physical appearance or the state of giving undue attention to things that most would deem to be of little value. However, in the Scriptures vanity is viewed in the contrast between physical matters of this life as opposed to the spiritual realities of eternity. Christ summed it up in these simple words:
Matthew 6:19-21 (KJV)
Lay not up for yourselves treasures upon earth, where moth and rust doth corrupt, and where thieves break through and steal: But lay up for yourselves treasures in heaven, where neither moth nor rust doth corrupt, and where thieves do not break through nor steal: For where your treasure is, there will your heart be also.
The apostle John put the subject in these simple words:
1 John 2:15 (KJV)
Love not the world, neither the things that are in the world. If any man love the world, the love of the Father is not in him.
By a strictly Biblical definition vanity has a way of just consuming lives. Paul put the matter in these terms:
Galatians 6:7-8 (KJV)
Be not deceived; God is not mocked: for whatsoever a man soweth, that shall he also reap. For he that soweth to his flesh shall of the flesh reap corruption; but he that soweth to the Spirit shall of the Spirit reap life everlasting.
It would be good for you to contemplate what the eternal harvest of your life will be. It is that harvest that you will have to live with for eternity!