John ends the first chapter with these five verses that are very different from the first five.  John makes observations that are "if/then" statements.  He makes it very clear that you can know absolutely whether you are a Christian or not.  And so can everyone else.

Verse 6.  "If we say that we have fellowship with him, and (then) walk in darkness, we lie, and do not the truth."

Verse 7.  "But if we walk in the light as he is in the light, (then) we have fellowship with one another, and the blood of Jesus Christ his Son cleanses us from all sin. "

Verse 8.  "If we say that we have no sin, (then) we deceive ourselves, and the truth is not in us."

Verse 9. If we confess our sins, He is faithful and just to (then) forgive us our sins, and to cleanse us from all unrighteousness."

Verse 10.  If we say that we have not sinned, we make him a liar, and (then )his word is not in us."

You may know all the scripture and all the right words, but live your life doing evil.  John says you are a liar.  Point by point he identifies what a hypocrite looks like.  A hypocrite is a person who says one thing and does another.

A Christian says what is right and true, and then does what is right and true.  One follows the other.  You either give your life to Jesus, or you don't.  You can't have it both ways.

What you say is not what identifies who you are.  It is what you do.

The church does not save you.  A preacher or a priest can't forgive you.  In Verse 9 it says: He forgives you.  Jesus.  God himself.  Jesus blood, in Verse 7, cleanses us from sin.  He died for us.  The Bible gives us the truth about salvation.  Trust Him.