Why do we need discernment when reading the Bible?

This is just my personal opinion.  When I compare the Gospels to the rest of the New T I find some differences that seem to be man added requirements and views.  Let's use these passages to explain what I mean.

1 John 2:1-6(NKJV)

My little children, these things I write to you, so that you may not sin. And if anyone sins, we have an Advocate with the Father, Jesus Christ the righteous. 

And He Himself is the propitiation for our sins, and not for ours only but also for the whole world.

Now by this we know that we know Him, if we keep His commandments. 

He who says, “I know Him,” and does not keep His commandments, is a liar, and the truth is not in him. 

But whoever keeps His word, truly the love of God is perfected in him. By this we know that we are in Him. 

He who says he abides in Him ought himself also to walk just as He walked.

Now Jesus Himself stressed over and over that salvation was a heart issue.  We are told that we are all sinners and all fall short of the glory of God.  We are also told that we will continue to sin even after we accept Jesus and will continue to need Jesus' forgiveness throughout our lives; and that is normal.  As long as our long term focus is on Jesus then the short term sins don't constitute a rejection of Jesus. 

John takes a different approach and I personally liken it to the "Jewish mother" trying to lay a guilt trip on her kids.  Or in other words manipulate her kids.   

According to John if we fail, as Jesus told us would happen even to the most devoted disciples, it proves that we never really believed in Jesus to begin with.  Let's test that theory.

So when Peter rejected Jesus 3 times as Jesus had said would happen, according to John this shows that Peter never truly believed.  Does that seem likely to you?  It doesn't to me. 

To me these verses seems to be more of a clumsy attempt to club people into behaving themselves.  Kind of like parents saying "if you kids don't behave yourself all year then Santa won't come".

Now if John had simply added "continually attempt" to his verses I think they would have been more in agreement with Jesus.

For example if John had said "Now by this we know that we know Him, if we continually attempt to keep His commandments." I think that would be more in the spirit of what Jesus said.  The continual effort, if sincere, indicates where the heart is truly at and Jesus has said repeatedly that that is the real issue to Him. 

Make sense?   

And that is why I think the discernment provided by the Holy Spirit while reading Scripture is so important!