Seeking the Best Night's Sleep

Early awakening still plagues my nights, which carries into my days.  The time of awakening has shifted from about 4AM to 2AM, though I can usually fall asleep again at about 4AM and go past my optimal wake time, which I set at 6:30AM.  The why still puzzles me.  I know where my routine breaks down, but with the schedule time shifted, staying fully upright through each day has not gone well either.  I tried installing a sleep monitoring app on my smart phone, going through about three before settling on one to try out.  My smart phone did a lot better than my not very smart iTOUCH  watch which claims to monitor sleep duration.  Reviewing the data from overnight added some insight, particularly the REM stages and deep sleep that I could not figure out otherwise.  It did fairly well.  What I considered wake time, that 2-4AM interval of repositioning and clock glances, it considered very light sleep.  Maybe it is.  When I eventually arise, not that long after my intended time, I do not feel overly sleep deprived, though crave some more snooze by late morning.  Coffee after cursory grooming perks me up.  Since the New Year, I have been trying to limit myself to two morning cups, but will consider an additional late morning addition.  And I am invariably able to exercise mid to late mornings.  So despite the interruption, I remain very functional.  More focus on what I do during the days that reflects on sleep, though I still do not appreciate the reason for the change in the last month or two after much success with formal sleep hygiene.  I'll just have to get more insight from the sleep monitoring app and trust its validity.