It is similar to bad breath in that the last person to know about it is one who has it. Now that is getting really rather personal, but it is true. Then it become more complicated in that we don't want to admit the deadly sin. Then it gets worse in that it is really tough to clean the bad habit up.
The Apostle Peter was pretending that he was following Jewish traditions according to Paul's writing in Galatians 2. Actually Peter was eating with the Gentiles and letting the letter of The Law go when he was around the Gentiles, but with when the Jewish leaders from Jerusalem came Peter became a pretender. He acted like he was truly following the traditions of The Law when he really wasn't. He shunned the Gentiles and acted pious as he begin to hold to old traditions, but he was just pretending. He was living a lie.
That is the sin of hypocrisy. It is a sin of pretending to be one thing when really we are not.
Here is some good news.
We can clean our act up and get real. We can deal with our fleshly ways and come into the blessing of the sunshine. That is where life is. It is in The Light of the Son.
Lord remove pretense from my life. Help me to live openly and honestly without pretense or hypocrisy. Let your truth go deep into my most inner being. Be real in my and in my life. May the words of my mouth and the meditations of my heart be acceptable in your sight, oh Lord, my strength, and my redeemer.