When I see such a door I ask myself "Am I okay here in this version of reality, at this moment?"
If the answer is "Yes", then I keep waking, if not I go through.
Every time I have done this when I have seen the shimmer, my life changes in some significant way related to whatever I happen to be going through at the time.
Sometimes I walk through these when I don't see the shimmer, but then I just look like a idiot usually. ;P
Edited by SteampunkScientist, 13 April 2019 - 11:58 AM.