"Man is free at the moment he wishes to be." - Voltaire

I think what this means is that if you hold yourself prisoner when you don't let go of things, or if you don't forgive someone for whatever reason. The moment you want to be free from all of that stress, all you have to do is to let things go. Be more mellow, do something relaxing or anything, really that will help you to let something go. Then you can hold on to that inner peace you now have.