I think this is true because I'm relieved of having to make decisions about people. When you love unconditionally it isn't your responsibility to grade your loved ones or to keep up with how they are doing. In recovery language it's called taking another person's inventory. When you love unconditionally, you're only responsible for your own inventory or inner work. This leaves me free to live in peace as long as I can forgive.
Forgiveness is the best and easiest way to get back into a state of peace.
I forgave myself for becoming upset, and I forgave Byron for taking offense at my upset, and I forgave everyone else who was involved, no matter how trivial their participation was. We can live in peace every day. See, I can remember when I used to withhold my love to punish a loved one. That doesn't mean I don't get angry or upset. Believe me, it gets easier with practice.