Most expositors of Scripture would answer that before the fall of man into Sin (which is a state not just on particular sin) that man was perfect and so able to be in God's Presence and communicate with Him. Once humans disobeyed God they fell from that perfect state. Now being imperfect they corrupted themselves and continued to fall into a state of sin. The sacrifice of Jesus on the cross was to take the consequences of sin from us and the ressurection and ascension into heaven was to restore us (through Jesus Christ)to communion with God. When Christ comes again (or when we get to heaven) that communion will be complete and we will be with the Lord forever in perfect communion with Him. I hope this ansers some of your questions.
Bless You
Mel
I'll need some time to ponder on what you have said. It still seems quite confusing, but I trust that there is a simple (and logical) answer.
Beautifully exposited!