A glass of white wine at dessert makes me sleepy fast.
But usually, I read a book, staying away from screens if I can (now I'm reading on my iPhone so I'm counterproductive), and at some point my eyes close by themselves. I don't look at what time it is.
Also, I have three alarms. I need to wake up at 6:15, so I have one alarm at 5:00, one at 6:05 and one at 6:15. The first one, I don't even realize that I woke up to turn it off. (It rings really loud so it's impossible that I've ignored it, orelse my whole family would wake up). After that one, that may seem very futile, I sleep like I've never slept. I cherish this whole hour. Then, the two successive alarms get me out of bed without problem.
Why not get that alarm that rolls around and forces you to get up and chase it to turn it off?