In order to keep that first commandment, your heart's desire must be to please Him. Thy word have I hid in mine heart, that I might not sin against thee. We break God's commandments when, rather than hiding His Word in our hearts because we love Him, we compromise it in our minds because we love ourselves more. We have put ourselves above God and, therefore have become gods unto ourselves. We have made ourselves idols.
Words are powerful things.
They can build up or break down. Science knows that sound travels through the universe for what they call infinity. In other words, it never goes away. Once released, your word becomes eternal. While God has not specifically named lying in His commandments, He has said that we should not bear false witness, which is lying.