I do not fully understand what time I am supposed to wake myself up for a WBTB. According to the DV tutorial on WBTB, one must wake up before a REM cycle is over. Each REM cycle lasts 90 minutes long, so I should wake up part way through one of those REM cycles, correct? However, even though I try to be consistent with the time I go to bed each day, I find that I fall asleep at different times each day, sometimes it takes 15 minutes, and sometimes it takes longer than 1 hour and a half. So that makes it very difficult for me to time my WBTB accordingly.
Any help would be appreciated.