"Forgive me if I have forgotten the Orthodox teaching. I thought you were in agreement with the Roman Catholics that the Holy Spirit abandons any body in a state of "major" (mortal) sin before the next confession, and then re-enters the body upon the completion of penance. It has been a while for me on this subject, so I admit to being a little fuzzy. :) I remember that you don't really get into the concept of "mortal" sin all that much, but I couldn't remember what the view was on when the Spirit indwells and whether He leaves, and then comes back, etc."
"A house roof is held up by the foundations and the rest of the building, and the foundation and the rest of the building are laid to hold the roof - since both are necessary and useful - and neither is the roof built without the foundations and the rest of the house, nor can foundations and walls without roof make a building fit to live in. So it is with the soul: the grace of the Holy Spirit is preserved by keeping the commandments, and the keeping of the commandments is the foundation laid for receiving the gifts of God's grace. Neither does the grace of the Holy Spirit remain in us without our obeying the commandments, nor can obeying the commandments be useful and salutary without Divine grace." +Symeon the New Theologian
Joh 14:16 And I will pray the Father, and he shall give you another Comforter, that he may abide with you forever;
Let your conversation be without covetousness; and be content with such things as ye have: for he hath said, I will never leave thee, nor forsake thee. (Hebrews 13:5 KJV)
Good thing the scriptures give us comfort. Clearly Catholic teaching doesn't.