A good testimony to forgiveness is in the prayer Jesus gave us. He taught us to pray, “…forgive us our tresspasses, as we forgive those who trespass against us…”
He would not have said that if He did not mean it, that forgiveness was possible.
But, He’s teaching us to forgive others, too.
Yes, there is sin all around us, in our thoughts, words, and actions, and in what we fail to do.
In Hebrews, it says to keep our eyes fixed on Jesus, the Author and Perfecter of our faith.
A Lutheran minister by the name of Dietrich Bonhoeffer wrote a book around 1937 called the Cost of Discipleship. Some non-Catholic and anti-Catholic stuff in there to be sure, but some good explanations, too.
He points out that when we are baptized we are like with Jesus on one side of the Grand Canyon, and everything else is on the other side. We act and relate to everything else through Jesus and because of Jesus. Everything is and should be different because we know Jesus Christ. Our temptations are different because we know that we have Jesus on our side and that He understands. Through Jesus we can control those temptations, instead of them controlling us.
I can write this to you not because of myself, but because of Jesus. And, you can receive it because of Him, not because of me. This shows that what may seem impossible is actually possible, if we open ourselves to it. He said, taste and see the goodness of the Lord. He said, repent and believe, not believe and repent. In other words, go to someplace different that you are used to, turn away from your sins and that will show you and help you to believe.