What is the Good News … of Forgiveness?

Passage: Matthew 6:15, 1 John 1:9

Jesus said; if you do not forgive others their sins, your Father will not forgive your sins (Matthew 6:15).
This is not Good News. In fact it is very bad news.
Why so? Because it links God’s forgiveness to our own. And that can’t be Grace. In fact it’s conditional. It’s not Grace, it’s Law.
So why did Jesus, the Lord of Grace, say this?