Quick answer
Ordinary work feeds you. Chasing what has nothing in it does not, and the verse calls that a failure of judgment rather than of luck.
Read both lines
The NKJV's footnotes sharpen both halves: "tills" is works or cultivates, and "frivolity" is literally vain things, meaning empty pursuits rather than harmless fun. The contrast is between a field, which is unglamorous and reliable, and schemes with nothing in them. The closing phrase is footnoted as literally lacks heart, the idiom this book uses for a person with no judgment yet, so the verse files chasing empty things with the failures of sense rather than with mere bad fortune. What it commends is the least exciting option available.
Related: Proverbs 28:19 · Proverbs 12:9 · Proverbs 6:32
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.