Hi Zoidar, the Lord calls the Pharisees "w
hitewashed tombs" ..
Matthew 23:23, which seems to say it best (to me anyway). They were all show in their appearing to others as beautiful, pious and clean on the outside, but their insides were the same as the inside of a beautiful tomb, "
full of dead men’s bones and all uncleanness". IOW, they did what they did to 'appear' righteous before men, but God knew that inwardly, they were full of hypocrisy and lawlessness ..
Matthew 23:28.
The Lord also told us that our own righteousness must surpass that of the Pharisees if we expect to have any hope of being saved .. e.g.
Matthew 5:20. Just to be perfectly clear, this is a group of men who were careful to/went so far as tithing minutia like mint, dill and cumin in their keeping of the Law ..
Matthew 23:23 (IOW, they were men who, like St. Paul ..
Philippians 3:5-6, were blameless/kept the Law perfectly .. the "letter" anyway). So the question is, how can anyone be saved, because who can possibly surpass that
The answer is, of course, Jesus Christ, who came here to do for us who believe what we could never do for ourselves
1) by living a perfect, righteous life before God (in both letter AND spirit) and
2) by dying on the Cross to make satisfaction to God for our sins so that we wouldn't have to. IOW,
2 Corinthians 5:21
21 He made Him who knew no sin to be sin on our behalf, so that we might become the righteousness of God in Him.
Christians have new hearts because God gave us new hearts and new spirits ..
Ezekiel 36:26, when He regenerated us/caused us to be "born again" ..
John 3:3, and by doing so, made us into wholly new creatures in His Son ..
2 Corinthians 5:17. So your heart IS clean because of Christ
Unfortunately, we will never be completely free from sin in this life (because of our old nature/self), but the good news is, the very same One who saved us in the first place has also promised to continue to grow us/mature us in our faith/in Christlikeness, through this life to Glory .. e.g.
Philippians 1:6, 2:13; cf Hebrews 7:25. So while your heart will not actually become "cleaner" than it already is (because you are already "in Christ"), it may seem like that to you since growing up in Him will increase your ability to recognize and avoid sinful behavior, and/or more quickly repent of it/ask forgiveness for it, when you do not ..
1 John 1:9
Those are my thoughts anyway. Hopefully they were at lest somewhat along the lines of what your were after

BTW, sorry for the essay length reply, it was not intended.
In Christ,
David
p.s. - speaking practically, you need to persevere in the basic Christian disciplines, in prayer .. e.g.
Philippians 4:6-8, in the knowledge and understanding of God's word .. e.g.
Joshua 1:8; 2 Timothy 2:15; 2 Timothy 3:16-17, in fellowship with other believers .. e.g.
Proverbs 27:17; Hebrews 10:24-25, in witnessing .. e.g.
Isaiah 43:10, and in service to others, all to a greater degree that you are doing now.
Memorizing verses/passages of the Bible can be VERY helpful as well because the HS can so much more easily guide/direct you when you know His word that well, and are able to access it that quickly
"How can a young man keep his way pure? By keeping it
according to Thy word. Thy word I have treasured
in my heart, that I may not sin against Thee"
Psalm 119:9,11