I've also noticed that even small amounts of alcohol at night can have a serious effect on quality of sleep, even just a couple of beers - nowhere near enough to cause a hangover, so you wouldn't necessarily notice the effect it's having until you cut it out completely.
I read on the internet (thus potentially to be taken with a pinch of salt) that even having a single beer in the evening can cause a worsening of the second half of your sleep. (Which is a bit weird as one might imagine the alcohol would be gone from ones system by then.)
I've tried total abstinence from alcohol and it really makes an AMAZING difference to how I feel the next day. (But perhaps it's just a placebo effect, since having read that internet article... YMMV)
From my personal experiences, having a quality roommate (not in same bed) forces me to adopt a normal sleep schedule. I don't want my activities to wake my roommate up and turn his day bad, so I sleep shortly after my roommate goes to bed. But when I live alone, I procrastinate my sleep, I would rather watch videos than go to bed, it wouldn't disturb anyone anyways, and the chances of having an abnormal sleep schedule becomes the norm.
Perhaps there is some psychological/social aspects to sleeping and what you and I have described falls into this aspect.
I've found this to be true. I also find I sleep more soundly and feel much better in the morning if I drink a big glass of water before bed too sort of "tank up"; otherwise I end up waking several times throughout the night. Oh, also the amount of light in a room is huge for me, which I didn't realize until I moved and had thick curtains installed.
I figured out that I sleep a lot better - especially when sharing a bed with her - when I omit drinking alcohol, even small amounts.
So maybe that's worth a try for people suffering from light sleep.