I have a theological question. Is the forgiveness of sins ultimately dependent on the sincerity of my confession? That sounds almost legalistic to me. And in my sinfulness, can I even be sure of the sincerity of my confession?
"Is the forgiveness of sins ultimately dependent on the sincerity of my confession?"
No. Our sins were forgiven in the once-for-all sacrifice on the cross of our Lord and Savior. God's act of sheer grace in applying that sacrifice to the forgiveness of our sins is complete in and of itself.
The sincerity of my confession is part of my hearing and understanding the "For you" in that act of God. What changes my life is not knowing that Jesus died to forgive the sins of sinners; it is in realizing that I am a sinner, and Jesus death on the cross brings about the forgiveness of
my sins. Then amendment of life is a response to that grace.
"Can I even be sure of the sincerity of my confession?" Again, no. "Lord, I believe. Help my unbelief." Thankfully, God does not dispense grace and forgiveness like a slot-machine! ("insert sincere confession in slot a, pull lever b, if you pass the sincerity test receive forgiveness! Otherwise, keep trying!")