Quick answer
Steady beats fast. The verse puts the same word on both halves, so the contrast is not between planning and not planning but between two tempos.
Read both lines
Both lines describe people who have plans, which is the detail that carries the verse. The hasty man is not lazy and he is not aimless; he is moving, and moving is what ruins him. The little word rendered "surely" appears in both halves in the Hebrew, so the parallel is exact and the outcomes are simply opposite. What the book is measuring is not effort but patience, and it has said the neighbouring thing about feet in a hurry at 19:2. Read as a promise this would be false, since diligent people go broke. Read as the shape of the thing, which is how this literature works, it is hard to argue with.
Related: Proverbs 19:2 · Proverbs 20:21 · Proverbs 28:20 · Proverbs 13:11
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.