Mr. Lewis makes a wise observation.*
Just because I know that forgiveness of those who do wrong will help free me from resentment (and that often the jumping off point for that forgiveness is the understanding that the people who do harm are themselves spiritually sick), that knowledge does not necessarily endow me with the ability to forgive.
Sometimes, all good knowledge can do is point the way.
We must still travel the distance and discover how to apply what we have learned.
Sometimes it makes sense to start small.
*Hat tip to Anne Lamott for reminding me of this quote.