"Therefore, if anyone is in Christ, he is a new creation. The old has passed away; behold, the new has come."
2 Corinthians 5:17 ESV
When God saves a person, he changes them from the inside. They become a different person. As covered in the article "Bound by sin, saved by grace", mankind is infected by sin and continually (and willingly) gravitates towards it. This is because we are slaves towards it and cannot overcome it via sheer willpower.
God, has promised that He will change the hearts of those He saves. He will give them a heart change that no longer desires to selfishly please themselves, but to please the One who created them. Furthermore, true born-again Christians will desire holiness as God is holy.
This is one of the marks or assurances that one is a true born-again Christian with the Holy Spirit dwelling within them.
"Then I will sprinkle clean water on you, and you will be clean; I will cleanse you from all your filthiness and from all your idols. Moreover, I will give you a new heart and put a new spirit within you; and I will remove the heart of stone from your flesh and give you a heart of flesh. I will put My Spirit within you and cause you to walk in My statutes, and you will be careful to observe My ordinances."
Ezekiel 36:25-27 NASB
Reader, if you are unsure whether you are truly saved, look to the Word of God. There are a number of things God has let us know would happen when we are saved. One of them is a permanent change of heart leading to a permanent change of desires.
Can you see this in your life?