One of the greatest challenges we face is to check our ideas/perceptions are grounded in reality. The brothers still had guilty minds (leading to them doubting Joseph's forgiveness) and they decided to try and manipulate him with their "father's words." (Some believers disagree and say Jacob did say these things).
The brothers were right in their belief that they sinned against Joseph and God. They were also correct in that they needed to confess their sins and needed to be forgiven or else they would be doomed. They also recognized they needed to serve the one they wronged.
Even though the brothers have been in Egypt for 17 years, they didn't believe Joseph when he said he forgave them.
Many people struggle with accepting God's forgiveness (causing them fear, anxiety, and them to avoid God). Satan will try to use old sins to haunt your mind and make you doubt God's love and mercy.
We may believe our sin is too evil or numerous for God to forgive us. We should remind ourselves that Jesus came to save us from our sins and no sin is greater than Him. Jesus has died for our sins, ones before and ones after we have accepted Him as a saviour, the price has been paid. If God can forgive you, there is nothing to stop you from forgiving yourself.
If you feel unworthy of forgiveness, do not be discouraged - forgiveness is a gift to those who do not deserve it! God is ready to extend mercy to those with repentance in their hearts.
There was much injustice and suffering in Joseph's life. He didn't retaliate against people who had wronged him, even when he rose to one of the highest ranks he could. He extended mercy and grace because he believed vengeance belonged to the Lord. Despite the hardships, Joseph was focused on God and His will not the wrongdoers. Their sin could not conquer God's plan for Joseph's life. We thank God that despite sin, He can do much good in the world.
Believers are not just made up of their pasts - there is a future so do not dwell on the past. Remind yourself about the Good News to stop doubting God's love.