The Spirit will convict as it did all through time,but will not be indwelling as with the church.
As far as Jesus Jesus saying he would never leave us. You should have learned in sundy scbool as a child.
We have to look at that passage I Context. Paul quotes that in Hebrews. He's quoting it from Joshua.
(KJV 1900): Only be thou strong and very courageous, that thou mayest observe to do according to all the law, which Moses my servant commanded thee: turn not from it to the right hand or to the left, that thou mayest prosper whithersoever thou goest. 8 This book of the law shall not depart out of thy mouth; but thou shalt meditate therein day and night, that thou mayest observe to do according to all that is written therein:
for then thou shalt make thy way prosperous, and then thou shalt have good success. 9 Have not I commanded thee? Be strong and of a good courage; be not afraid, neither be thou dismayed: for the Lord thy God is with thee whithersoever thou goest.
Notice the condition. Joshua was not to depart from the Law. We see what happened when Israel sinned shortly after this.
Joshua 7:10–12 (KJV 1900): And the Lord said unto Joshua, Get thee up; wherefore liest thou thus upon thy face? 11 Israel hath sinned, and they have also transgressed my covenant which I commanded them: for they have even taken of the accursed thing, and have also stolen, and dissembled also, and they have put it even among their own stuff. 12 Therefore the children of Israel could not stand before their enemies, but turned their backs before their enemies, because they were accursed: neither will I be with you any more, except ye destroy the accursed from among you.
We see that God was them as long as they kept His commands, they obeyed the covenant. It's the same with Christians. The book of Hebrews was written to encourage Jewish believers to remain faithful in the face of persecution. Paul was reminding then that God is faithful as long as we are. If we break the covenant God is no longer required to uphold His end.