“What assurance do you have that your sins were forgiven?”
Can’t answer for kindred, but...
“14For all who are led by the Spirit of God are sons of God. 15For you did not receive the spirit of slavery to fall back into fear, but you have received the Spirit of adoption as sons, by whom we cry, “Abba! Father!” 16 The Spirit himself bears witness with our spirit that we are children of God, 17and if children, then heirs—heirs of God and fellow heirs with Christ, provided we suffer with him in order that we may also be glorified with him.” — Romans 8
That said, the 1689 Baptist Confession of Faith says (and I agree - it mirrors my own life closely):
18.1 Temporary believers and other unregenerate people may deceive themselves with futile and false hopes and unspiritual presumptions that they are in favour with God and in a state of salvation, but their hope will perish. [1] Yet those who truly believe in the Lord Jesus, and love him in sincerity, and endeavour to walk in all good conscience before him, may be certainly assured in this life that they are in the state of grace; they may rejoice in the hope of the glory of God, knowing that such hope will never make them ashamed. [2]
1. Jeremiah 17:9 Matthew 7:21-23 Luke 18:10-14 John 8:41 Ephesians 5:6-7 Galatians 6:3,7-9
2. Romans 5:2,5 Romans 8:16 1 John 2:3 1 John 3:14,18-19,24 1 John 5:13 2 Peter 1:10
18.3 This infallible assurance is not an essential part of faith, for a true believer may wait a long time, and struggle with many difficulties before obtaining it. [1] Yet we may obtain it without extraordinary revelation and by the right use of ordinary means, for we are enabled by the Spirit to know the things which are freely given to us by God. [2] Therefore it is the duty of everyone to be as diligent as possible to make their calling and election sure, so that their hearts may be enlarged in peace and joy in the Holy Spirit, in love and thankfulness to God, and in strength and cheerfulness in carrying out the duties of obedience. These duties are the natural fruits of this assurance, for it is far from inclining people to loose living. [3]
1. Acts 16:30-34 1 John 5:13
2. Romans 8:15-16 1 Corinthians 2:12 Galatians 4:4-6 with Galatians 3:2 1 John 4:13 Ephesians 3:17-19 Hebrews 6:11-12 2 Peter 1:5-11
3. 2 Peter 1:10 Psalms 119:32 Romans 15:13 Nehemiah 8:10 1 John 4:19,16 Romans 6:1-2,11-13 Romans 14:17 Titus 2:11-14
Then why would our Lord have entrusted the forgiveness of sins to His Apostles?