Quick answer
Two different failures with two different costs. Hot temper produces foolish acts; cold scheming produces enemies.
Read both lines
The Hebrew for "quick-tempered" is literally short of nostrils, an idiom about a fuse, and it will be answered at verse 29 by its opposite, the person who is long of nostrils and therefore slow to wrath. What the verse adds by pairing the hot man with the calculating one is a distinction worth keeping: the first is a problem of speed and the second of intent. The temper produces embarrassment; the scheming produces hatred. Neither is defended, and the book will spend more words on the second.
Related: Proverbs 14:29 · Proverbs 12:2 · Proverbs 6:18
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.