What if it were easy? There is probably at least one person in your life whom you find it very easy to forgive. This is a person you love: a spouse, a friend, a parent, a child, somebody. If this person goes around being horrible to others and to you, you don't just sit there and take it--for her sake, you tell her why what she's doing is wrong. You do your best to stop her from acting wrongly. This even though she's the person you forgive quicker than anyone else.
From this experience we learn one important thing: Challenge isn't separate from love. You adore her, therefore you try to stop her when you think she might harm herself or others. Love doesn't mean, "Okay honey, do whatever you want, I don't care."
Okay... so try to apply this, analogously, to people you don't immediately love. What if you loved them? What if it were easy to forgive them?
You still wouldn't pretend like they had never done anything wrong. Forgiveness doesn't mean pretending the wrong never happened. It doesn't mean that you can't take the wrongdoing into account when trying to figure out if you should trust the other person with a confidence, or a $20 bill.
This sort of fits in with something that came up in a recent conversation, in which it was pointed out that we know how it is that God can forgive someone -- all sin is sin against God -- but it's less clear what it means for one human to forgive another. When God forgives, there's a change in the one forgiven. When we forgive, what really happens?
There's a lot that can be said about that, but we might pause for a moment to consider the words "we know how it is that God can forgive someone." How God forgives is through the crucifixion and death of His Son. So perhaps, sometimes, forgiveness can't be easy, no matter how holy the person is. Perhaps, sometimes, when forgiveness is easy, we aren't forgiving so much as declaring our indifference. Perhaps, sometimes, when we say, "I forgive you," we really mean, "You did not injure me."