(lessons from Proverbs 15)

About a week ago my tongue got away from me when dealing with a vendor who happens to be a compulsive liar. I had finally had enough. I was ashamed of myself almost immediately afterwards and went to the Good Book in order to find a solution to my problem. (this happened about 5 years ago with another vendor/partner, so I saw a pattern starting)

Anyway, the scripture I accidently opened up was Prov 15:1-2
"A soft answer turns away wrath, but a harsh word stirs up anger. The tongue of the wise uses knowledge rightly, but the mouth of the fools poors forth foolishness."

Also: 15:15
"All the days of the afflicted are evil, but he who is of a merry heart has a continual feast."

Thus, from these scriptures it appears that a wise person has a merry heart and a soft tongue which can heal (or crush) the spirit of another. Do you agree, and does anyone have any suggestions for managing the use of words in the midst of a heated argument?
Quote from a book/video on Emotional Intelligence: "A fifteen second amygdalia hijacking can ruin the rest of your life."

Edit #1 - 15:15 directed me to 17:22. Together they kind of help to better understand the meaning of life, don't you think?

Prov 17:22 "A merry heart does good, like medicine, but a broken spirit dries the bones."

More relevent verses -

Prov 15:22 "Without counsel, plans go awry, but in the multitude of counselors they are established."

Prov 16:29 "A violent man entices his neighbor, and leads him in a way that is not good."

Prov 17:5 "He who is glad at calamity will not go unpunished."

Prov 17:14 "The beginning of strife is like releasing water; therefore stop contention before a quarrel starts."

P.S. for Scott2
Prov 17:9 "He who forgives and forgets (covers) a transgression seeks love, but he who repeats a matter separates friends."