Why do some people struggle to trust in God's grace?

The struggle to trust in God's grace often stems from a misunderstanding of the gospel and God's holiness. As presented in Romans 10, some individuals, much like the religious lost of Israel, may possess zeal but lack the knowledge of God's righteousness. They attempt to establish their own through works of morality or religion, rather than receiving righteousness as a gift through faith in Christ. In Isaiah 55:2, the call to 'eat that which is good' suggests that those who do not turn to the Word of God remain in ignorance and cannot see the sufficiency of grace offered in Christ.