"...and grant me Thy law graciously." (Psalms 119:29b)
It didn't happen overnight (see Luke 21:19).
I still remember the day, in my late teens, that I realized just how far from God I felt by having chosen, at a young age, to be dishonest with Him, myself and other people (it's God's grace that let's you see how bad things are, by the way). It seemed it would take an eternity to become what I knew I could have been a long time ago. I may have been young when I accepted the Lord and became a Christian, but God saw my faith was real and so He honored my decision and declaration. But sin is sin and lies are lies, black or white. I won't get in to the specifics of influence that led me to hide but I know that my will and misused faith were strong enough to produce wrong effects that became clear later in life.
The second part of Psalms 119:29 provides the antidote to a baseless and ultimately godless life. David asks God to give him, to grant him His law. The Psalmist (whomever it is, I vote David), it seems, is saying, "God, I want Your truth. I've discovered, in Your light, that the truth is not in me, (remember, light reveals darkness—see Psalms 63:9) so I need you to grant it to me." Better late than never.
Make an effort to renew your mind to God's standard of truth (see Romans 12:1-2) and you will find, not only your thinking clear up—"thy thoughts shall be established", as it says in Proverbs (16:3)—but your true character shine through. Your individuality as diffused through your true station as a "new creation", as it says in 1 Corinthians 5:17.
If any of the above (or part one) resonates with you, pray Psalm 119:29 to God. He'll take you by the hand (see Isaiah 41:13) and lead you back through the tangled forest of your bad decisions, teaching you every step of the way, "precept upon precept" (Isaiah 28:10). This is what He did for me.
And don't forget to tell Him you love Him.