Quick answer
Character functions as navigation. What a person is made of ends up steering them, in one direction or the other.
Read both lines
Both halves make the same structural claim with opposite outcomes: the thing inside a person does the driving. Integrity here is wholeness, a life without a hidden compartment, and the verse says it guides, which is a gentler verb than the second line's. Crookedness does not guide the unfaithful; it destroys them. That asymmetry is deliberate. One way of living gives you a direction, and the other eventually gives you a result you did not choose, and neither requires any outside agent to arrive.
Related: Proverbs 11:5 · Proverbs 10:9 · Proverbs 13:6
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.