Trustworthy people are very rare.
Proverbs 20:6
Many a man proclaims his own loyalty, but who can find a trustworthy man?
Even if we've done the right thing, we need to ask ourselves if we did it for the right reason.
We are sinners, so yes, we are bound to do the wrong thing. We need to study God's Word and examine our actions and thoughts in light of that Word. Then we will see our sins clearly. And if we come to God with our sin, confessing and repenting of our sins of unfaithfulness toward Him and toward people, then He will forgive us and help us to repent. This is the reason He sent His Son Jesus into the world.
1 John 1:8-9
If we say that we have no sin, we are deceiving ourselves and the truth is not in us. If we confess our sins, He is faithful and righteous to forgive us our sins and to cleanse us from all unrighteousness.
Your first paragraph applies to those who have not yet been born again, i.e., accepted Christ as their savior. Those of us who have accepted Christ are no longer sinners; we are God's children in Christ.
God has already forgiven Christians for all their sins, past, present, and future. If we continue confessing and repenting of our sins then we are denying the finished work of the Cross.
Your quote from 1 John 1 is interpreted incorrectly (as many do). John was writing the beginning of his letter to those people who were
not yet Christians. 1 John 1:3 makes this perfectly clear: "We proclaim to you what we have seen and heard, so that you also may have fellowship with us. And our fellowship is with the Father and with his Son, Jesus Christ."
Later in the same letter, addressing Christians, he wrote
1 John 2:12-14, "I am writing to you, dear children,
because
your sins have been forgiven on account of his name.
I am writing to you, fathers,
because you know him who is from the beginning.
I am writing to you, young men,
because you have overcome the evil one.
I write to you, dear children,
because you know the Father.
I write to you, fathers,
because you know him who is from the beginning.
I write to you, young men,
because you are strong,
and the word of God lives in you,
and you have overcome the evil one."