Your thoughts re alarm clock etc are uncannily congruent with mine! So many times I've invented reasons in the night to turn off the alarm. So I gave up trying to fight my true programming.
If you say you are going to get up and go the night before then there is no excuse in the morning.
Ah, sometimes an ill child can disrupt sleep enough to invalidate the best intentions. But that's happened twice in about 3 years do you are indeed correct.
Maybe no valid excuse, but if you can't find an excuse at all, you're obviously very bad at making them. I have come up with hundreds.