If people are capable of committing sin, everyone suffers during their lives. They disappoint God and let him down frequently.
Not if they believe God. When a person accepts God's offer to make him / her a family member, God gives then a new spirit which cannot sin.
This is the "YOU" that God interacts with after regeneration. God is not disappointed in my new spirit he installed at salvation. This is the ultimate meaning of circumcision. The old spirit is sliced off, like a foreskin, and a new spirit is installed. This is called the circumcision of the heart.
Col. 2 - "For in him the whole fullness of deity dwells bodily, 10and you have been filled in him, who is the head of all rule and authority. 11In him also you were circumcised with a circumcision made without hands, by putting off the body of the flesh, by the circumcision of Christ,
12having been buried with him in baptism, in which you were also raised with him through faith in the powerful working of God, who raised him from the dead. 13And you, who were dead in your trespasses and the uncircumcision of your flesh, God made alive together with him, having forgiven us all our trespasses, 14by canceling the record of debt that stood against us with its legal demands.
This he set aside, nailing it to the cross. 15He disarmed the rulers and authoritiesb and put them to open shame, by triumphing over them in him."
1 John 3: 9 - Whosoever is born of God doth not commit sin; for his seed remaineth in him: and he cannot sin, because he is born of God.
Deuteronomy 30:6 ESV
And the Lord your God will circumcise your heart and the heart of your offspring, so that you will love the Lord your God with all your heart and with all your soul, that you may live.
Romans 2:28-29 ESV
For no one is a Jew who is merely one outwardly, nor is circumcision outward and physical. But a Jew is one inwardly, and circumcision is a matter of the heart, by the Spirit...