Quick answer
A crooked interior and a crooked mouth arrive at the same place. The verse pairs the source and its output.
Read both lines
The NKJV footnotes "deceitful" as crooked, and the geometry is this book's usual: lines that do not run true. What the pairing establishes is a sequence rather than two separate faults, since the heart in the first line is where the tongue in the second gets its material. "Finds no good" is a quiet way of describing a life that keeps coming up empty without any single disaster to point at, and it is a bleaker outcome than punishment because there is nothing to appeal.
Related: Proverbs 11:20 · Proverbs 4:23–24 · Proverbs 6:12
New King James Version®, Copyright © 1982, Thomas Nelson. All rights reserved. Full copyright information. Scripture provided by API.Bible.
Go Deeper
If this verse has been used to put weight on you that it was never carrying, ask about it directly.