The near-twin of 16:2, which differs in one noun.
Quick answer
Self-assessment is not assessment. The verse grants that everyone believes their own case and then names who is actually doing the measuring.
Read both lines
The first line is not an accusation, it is a description of the equipment: a person evaluates his own conduct with the only eyes he has. That is why the second line has to introduce a different instrument entirely. The verb is from weighing, a scale rather than a glance, and 16:2 said the same thing with spirits where this one says hearts. What makes the pairing useful is that the chapter has just said God turns a king's heart and now says He weighs everyone's, so the two verses together describe a God involved with interiors rather than only with outcomes. Two chapters back the book asked who could call his own heart clean. This one explains why nobody can answer.
Related: Proverbs 16:2 · Proverbs 20:9 · Proverbs 16:25 · Proverbs 21:8
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.