So Sleepy

I've been trying to figure out why I can fall asleep right away if I'm taking a mid day nap but when it's time to go to sleep for the night it doesn't seem to come as easily?  

I mean these days I try to only take a nap if I'm desperately tired/sleepy mid day but still, I seem to just slip off to sleep right away.  I've tried to "trick" myself into thinking I'm "just taking a nap" in bed at night and I don't think that it works but maybe I'm falling asleep and forgetting that I did it?

These days *if* I do nap I set an alarm.  Usually 15 minutes, sometimes five more or five less.  I'll often have the alarm go off and reset it.  Maybe another 10, maybe another 15.  Sometimes I'll do this for an hour, these little naps without letting myself be deeply asleep for too too long.  My attempt at not completely messing up my night time sleep, but often it does anyway but sometimes I just need that day nap, you know?

Now, to be fair, napping when sick is a whole different ball game and I just do what my body needs when that's the case.

The other morning I found myself wondering if when I stay in bed in the morning, despite having sort of "woken" a bit, am I napping or am I staying asleep from the night?  It's probably six of one half a dozen of the other but it's a funny thought to have as I try to keep myself from becoming fully awake.  Or maybe "fully aware of my bladder" as the case may be!  I mean often, that's what makes me stop having mini naps during the day, I am doing my best to be hydrated and that results in needing to go sooner or later, you know?

But yeah.  If I can fall asleep quickly for a nap, why is the night time sleep different and when I'm staying in bed in the morning am I napping or "staying" asleep?