These are intensely practical things: how to know the comfort of the Gospel. You need to know your sinfulness. There are, of course, other things to know too, but without a sense of sin you will have little sense of salvation (Luke 7v36ff, esp. vv45-47)

Many people do not see their sinfulness. They say "I am not perfect, but no one is". That is not a confession of sinfulness, but a permissiveness that acquits oneself. It makes light of any fault.

The real trouble is that self judgement is made by the wrong standard. The criteria used are the standard of others conduct or a self invented standard. The standard which will tell the truth and find us out is the law of the Lord (Romans 7v7). Apart from this we do have a conscience that will indicate something (Romans 2vv14-15), but that faculty needs awakening and fine-tuning. We need to look into the word of God which is a mirror to reflect the real state of our hearts (James 1v23-24).

We do not have to look to the Old Testament commandments alone. Jesus has interpreted those commandments. He has interpreted NEGATIVELY as in Matthew 5vv21ff, and POSITIVELY as in Matthew 22vv37-39. He declares that it is insufficient to simply avoid literal murder or adultery and that hatred and lust - the sins of the heart and mind - are sins. He requires that we love God with all our heart, soul and mind. Now, have you loved God with all your heart? That seems a great deal. Not only heart but soul and mind too - all of every faculty. How high is God's standard! It is perfection. The pass mark is 100% and we fail to reach that glorious ideal (Romans 3v23).

We do not just slightly fall short. We are altogether sinful (Romans 3vv10ff). It would not be too strong to say that we hate God apart from a work of the Holy Spirit. See the resentment of men when it said that God has absolute sovereign rights over their lives. Christ would not have died on the cross to save if we were not in serious trouble.

You need to appreciate your real predicament. Which man are you most like: the Pharisee or the tax collector of Luke 18v14? It is not the one who thanked God for His grace in his life that Christ commended, but the one who begged for mercy to a sinner.