An "unabridged" version means not shortened, complete, not missing any text. A shortened version of a novel or of a dictionany is the opposite of this: it is abridged. The verb "abridge" itself means to shorten without a loss of content.
It allows him to move further on and figure out why things happened the way they did. And allows him to heal because it takes the stress and gets him out of the rut, that is caused by not forgiving himself.
