A tough prayer

In school assemblies, we've been going through the Lord's prayer.
The opening line, 'Our Father in heaven' isn't too difficult even for 5 year-olds to understand. And once we'd talked a bit about respect, it wasn't too difficult to grasp the main point of 'hallowed be your name'.
But in a couple of weeks' time we get to 'forgive us our sins as we forgive those who sin against us'. On the face of it, this is quite straightforward, and there are plenty of easy illustrations.
And yet this is one of the hardest things to say to God with complete honesty. Are we really content that he forgives us as we forgive others? Don't we really want him to forgive us more easily, more quickly, more fully that we forgive others? But Jesus is uncompromising:

If you forgive others their trespasses, your heavenly Father will also forgive you, but if you do not forgive others their trespasses, neither will your Father forgive your trespasses.

People sometimes talk too easily about God's unconditional love. But here there is clearly a condition attached to our receiving forgiveness from God - we must forgive others.
But then Jesus is talking to people who have begun to understand that God gives us

...strength to comprehend with all the saints what is the breadth and length and height and depth, and to know the love of Christ that surpasses knowledge, that you may be filled with all the fullness of God.

And surely such forgiveness as Jesus expects us to show is only possible because he has begun a work of grace in us, and has begun to give us the knowledge of the full extent of his love for us.

So it will be one thing to talk to the children about forgiving each other, but quite another for them to fully appreciate and experience the forgiveness and love of Christ so that they are empowered to forgive as they would like to be forgiven. My prayer is that they will indeed experience the grace of God.
But my prayer also is that adult Christians will be able to model this kind of living and forgiving.