Let's look at the second book of John..  It has only one chapter.  Only thirteen verses.  But when John wrote this letter, he was trying to say something very specific.  First, he wanted the lady to whom he was writing to be reminded that what she and her and her children had heard concerning Christ was true.  He uses the word 'truth' five times in four verses.

II John 1:1-4  "The elder (John) unto the elect lady and her children, whom I love in the truth; and not I only, but also all those that have know the truth;  For the truth's sake, which dwells in us , and shall be with us for ever.  Grace be with you, mercy, and peace, from God the Father and from the Lord Jesus Christ, the Son of the Father, in truth and love.  I rejoiced greatly that I found your children walking in truth, as we have received a commandment from the Father."

This woman is blessed.  Her children are living in the truth.  Whoever she is, in the apostle John's eyes, she has certainly been elevated to a position of honor because of the life she is living.  He tells her that he, and all those who know the truth, love her in the truth.  John gives her a special blessing of grace, mercy and peace.  Not only from him, but from God the Father and Jesus the Son.

Truth.  We all want to know the truth.  John knew what it was and was busy writing letters, visiting churches and living the rest of his life spreading the truth to anyone who would listen.
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In thirteen verses, John will sum up some important truths for your life, my life, and the life of the lady and her children.  All of us.  The truth never changes.