Quick answer
There is real joy in saying the right thing at the right moment. The NKJV footnotes "in due season" as literally in its time, and timing is most of what makes a word good.
Read both lines
The first line uses the same word for "answer" that opened the chapter at 15:1, so the two verses frame the same skill from opposite ends: there, the answer that cools a conflict; here, the answer that lands so well the speaker himself feels the gladness of it. The second line abandons observation altogether and simply exclaims, which is rare in this book and worth hearing. The sages are not describing eloquence. A word in its time is often short and unremarkable in transcript, and its power is almost entirely in the moment it arrived, which is why 25:11 reaches for apples of gold in settings of silver to describe it. Most people can remember such a word spoken to them years later, and could not tell you anything else about the day.
Related: Proverbs 15:1 · Proverbs 25:11 · Colossians 4:6
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.