I love this verse and memorized it long ago, but it is in the Old Testament. Now we are under the New Covenant after Christ's resurrection.

I am a new creation in Christ so my true spirit/heart is no longer deceitful...If I still had that old deceitful nature, how could I be united with Christ? He only unites Himself with holy beings.

I learned this at network220.org/books and it changed my life. I used to hate myself thinking I still had a sinful, deceitful nature. Now I can love myself knowing my old sin nature was exchanged for a holy new nature. Galatians 2:20