Grace - or in Latin: Graci, to give thanks.
To be in a state of Grace, in the Eastern mind, if we want to stick with this notion, is to be in a state of perpetual thanks. To be in a state of "mortal sin," or in the Eastern mind - Grave (as opposed to Transgressions), is to be in a state of such disunity that confession is needed to restore one's communion w/ the community (the Church).
Having talked with peers, if one looked at the definition; and how it's applied, it takes a lot to be in such a definition. The falling from the mark is so deliberate, so intentional, that one falls down the path, that the Eucharist will only be to one's detriment (per the Pauline Epistles).
A good book to read, if not having read it, is Shown To Be Holy: An Introduction to Eastern Christian Moral Thought. It's affordable, and well put together. It has been recommended by others in this forum, too.