Contradiction with Philippians 4:6
Encourages thankfulness and prayer in every situation, whereas Proverbs 23:8 mentions vomiting up what you've eaten and wasting words.
Philippians 4:6: Be careful for nothing; but in every thing by prayer and supplication with thanksgiving let your requests be made known unto God.
Contradiction with Proverbs 17:28
Advises keeping silent to appear wise, which contrasts with the negative connotation of speech and action in Proverbs 23:8.
Proverbs 17:28: Even a fool, when he holdeth his peace, is counted wise: [and] he that shutteth his lips [is esteemed] a man of understanding.
Contradiction with Proverbs 15:13
States a merry heart makes a cheerful countenance, contrasting with the unpleasant action of vomiting mentioned in Proverbs 23:8.
Proverbs 15:13: A merry heart maketh a cheerful countenance: but by sorrow of the heart the spirit is broken.
Contradiction with 1 Thessalonians 5:18
Urges giving thanks in everything, unlike the negative experience of losing what you have eaten as suggested in Proverbs 23:8.
1 Thessalonians 5:18: In every thing give thanks: for this is the will of God in Christ Jesus concerning you.
Contradiction with Proverbs 15:1
Promotes a soft answer turning away wrath, differing from the outcome of wasted words and a symbol of unrest in Proverbs 23:8.
Proverbs 15:1: A soft answer turneth away wrath: but grievous words stir up anger.