If we change the way we think, we will change the way we live.
Another way to say this is... If you think the way you used to think, you'll do the things you used to do.
or
If you think the way you always think, you'll do the things you always do.

1 Oh, what joy for those whose disobedience is forgiven, whose sin is put out of sight! 2 Yes, what joy for those whose record the Lord has cleared of guilt, whose lives are lived in complete honesty! 3 When I refused to confess my sin, my body wasted away, and I groaned all day long. 4 Day and night your hand of discipline was heavy on me. My strength evaporated like water in the summer heat. 5 Finally, I confessed all my sins to you and stopped trying to hide my guilt. I said to myself, "I will confess my rebellion to the Lord." And you forgave me! All my guilt is gone.

7 "Blessed are those whose lawless deeds are forgiven, And whose sins are covered; 8 Blessed is the man to whom the Lord shall not impute sin."

12 For I will be merciful to their unrighteousness, and their sins and their iniquities will I remember no more. 13 In that he saith, A new covenant, he hath made the first old. Now that which decayeth and waxeth old is ready to vanish away.

16 "This is the covenant that I will make with them after those days, says the Lord: I will put My laws into their hearts, and in their minds I will write them," 17 then He adds, "Their sins and their lawless deeds I will remember no more."