Quick answer
Money that arrives too fast and too early tends not to last. The verse is about the manner of acquiring, not about the amount.
Read both lines
The Hebrew word behind "hastily" carries a scribal variant, and both readings point the same direction, toward something seized or rushed rather than received in course. Which is what makes the verse specific: an inheritance is by definition something you did not earn, so the problem cannot be the unearnedness. It is the haste. The second line places the outcome at the end, which is where this book characteristically puts the verdict, and it declines to say what goes wrong. It says only that whatever arrived early does not carry a blessing forward, and the reader is left to supply the examples, which most readers can.
Related: Proverbs 13:11 · Proverbs 20:17 · Proverbs 28:20 · Proverbs 19:2
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.