How do we know repentance is true?

Genuine repentance involves a fundamental shift in perception concerning God's holiness, Christ's righteousness, and the sinner's condition. It is not merely behavioral change but a deep acknowledgment of one's inability to attain righteousness apart from Christ. This leads to a resolute turning away from any inclination to establish personal righteousness, hence demonstrating that the individual's faith is robust and genuinely saving. The absence of such repentance would indicate that the faith held is insubstantial and not rooted in true understanding.