When we do sin we have an advocate with the Father 1 John 1:9 and God disciplines those who belong to Him.
Hebrews 12:5-7 "…5 And you have forgotten the exhortation that addresses you as sons: “My son, do not take lightly the discipline of the Lord, and do not lose heart when He rebukes you. 6 For the Lord disciplines the one He loves, and He chastises every son He receives.” 7 Endure suffering as discipline; God is treating you as sons. For what son is not disciplined by his father?"
Never think a believer never sins, it will cause pride in those who try so hard in their flesh to be perfect and it will cause harsh judgment on anyone who falls but repents.
1 John 1:8-10
"If we say we have no sin, we deceive ourselves, and the truth is not in us. If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness. If we say we have not sinned, we make him a liar, and his word is not in us."
These passages were written to born again believers not to the unsaved.
The more we confess our sin soon after we catch ourselves the more we grow in holiness and a change of behavior. We are not sinless but we do sin less, that is if our repentance was genuine and Christ changed us.
Those who become angry at being confronted with their sinful attitudes are those who have not been born-again. Those who are born again and are stubborn will be severely spanked to show them their need to confess their sin to be cleansed of it.
Without confession of sin there is no Spiritual and emotional growth, there is only immaturity and the quenching of the Spirit of God. Those who ignore the Holy Spirit conviction will cause the Spirit to go silent and leave us without instruction and without help.
1 Thessalonians 5:19-22
"19 Do not quench the Spirit, 20 do not utterly reject prophecies, 21 but examine everything; hold firmly to that which is good, 22 abstain from every form of evil."