One of the most quoted verses in the book, and one of the few places Proverbs describes waiting from the inside.
Quick answer
Waiting for something that does not come makes a person ill, and the verse says so without scolding anyone for it. The relief, when it arrives, is life-giving.
Read both lines
What makes this verse remarkable is that it validates the feeling. Scripture is often read as telling people to wait patiently and cheerfully, and here the plain observation is that deferred hope makes the heart sick, a word for real illness rather than mild disappointment. No fault is assigned. The second line then reaches for the book's strongest positive image, the tree of life, used of wisdom at 3:18 and of a righteous life at 11:30, and applies it to a longing finally satisfied. The verse takes both halves of the human experience seriously: the waiting is genuinely bad, and the arriving is genuinely good.
From this side of the cross
Proverbs describes what waiting does to a person and stops there, which is honest. Paul writes about the same sequence and adds where it goes: tribulation produces perseverance, perseverance character, character hope, "now hope does not disappoint, because the love of God has been poured out in our hearts" (Romans 5:3–5). That is not a correction of the proverb and not a reason to stop calling the sickness what it is. It is the claim that one particular hope has an arrival date, and that the waiting is not aimed at nothing.
Related: Romans 5:3–5 · Proverbs 3:18 · Proverbs 11:30 · Proverbs 13:19
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.