Read Matthew 23:13-36. Notice the word Jesus used to describe the scribes and Pharisees five times - "blind". What were the scribes and Pharisees blind to? They were blind to their sin problem. They were trying to be righteous by obeying the Law of God and were powerless to overcome the desires of the flesh inwardly. Even though they became good at the public appearance of living according to Law externally and the people perceived them as righteous, they were full of sinful desires that oozed out of their lives. Jesus described them as outwardly clean, inwardly full of greed and self indulgence.
An illustration from my life. Let's say I'm a Pharisee with a love for potato chips and dip. The potato chips and dip have a negative effect on my health by adding unwanted pounds. In public I would say no to eating potato chips at gatherings and tell the people I avoid the chips by not stocking them in my house. People would say I was so righteous. However, the sin in me would crave to taste the chips and dip. As a Pharisee, I would sneak out, buy the chips and dip and secretly devour the whole bag of chips and container of dip and destroy all evidence so I wouldn't be caught. I would never let people know I was indulging myself so I could continue to appear righteous in their sight and praised for my self-control. My outward shows of asceticism and severity to my body by not eating or buying chip and dip publically had no value in stopping my indulgence in sinful behavior
Let's say one day the Lord caused me to see I had a sin problem that outward public discipline alone would not overcome. I was led by the Lord to repent of my sin, believe the gospel and receive the Holy Spirit of God to live in me. I still crave to eat potato chips and dip, but now I confess my craving publically and my inability to overcome this craving that is ruining my health. I admit to the Lord that I am powerless to overcome my sin of over eating chip and dip. I attempt to not eat chip and dip publically and privately to excess expecting the Lord to fulfill my attempt with His power. I find that I am gaining freedom from indulgence of my sinful nature to eat a bag of chips and a cart on of dip privately. I no longer buy the chips and dip, not to appear to have self-control, but because the Lord Jesus is changing my desire and empowering me to overcome my sinful self-indulgence.
As a Pharisee, I sought to appear righteous and receive the praise of people and I indulged my sin secretly. As a believer in Jesus Christ I was made righteous by repenting of my sin and believing the gospel and was able to live righteously by faith in Jesus - by attempting to do what is right expecting Jesus to fulfill my attempt with His power. How are you dealing with inward sin? Are you publically doing what is right, but privately indulging your sinful cravings? - or - Are you admitting your inward sin, repenting of it and overcoming the indulgence of sinful desires by faith in Jesus? Don't be blind and not see your sin problem. Let the light of the gospel help you see and overcome sin by belief in Jesus.
Some scriptures to read. Romans 7:23-8:13; 9:30-32; Philippians 3:1-11; Colossians 2:20-23