I used to think my mood swings could be explained, too. I had all kinds of reasons for them: work-related stress, the weather (a common one), interactions with other people, travel, not sleeping enough, etc. Turns out a few of them were correct, and in fact all of them were accurate some of the time, but the reality was that a lot of the time my explanations weren't explaining anything.

Being bipolar doesn't mean your mood only changes randomly. It means that certain things will trigger mood swings, but sometimes it's also completely out of your control and something you can't predict at all.

So the best strategy is typically to take your meds against the random/unpredictable stuff, and know and avoid or work on your triggers to make sure the predictable stuff doesn't undermine you. For example, I have an 11 PM bedtime to avoid problems with sleep cycle getting off track and not enough sleep, because that's a sure-fire way to trigger hypomania for me. A bipolar girlfriend eats a highly restricted diet because blood sugar fluctuations set off mood swings for her, while I only get headaches and feelings of apocalypse when my blood sugar gets low (that's quite bad enough for me, thanks - and oddly, I'm the one diagnosed as hypoglycemic!)

Bunch of ideas and thoughts at night = "flight of ideas"/"racing thoughts" which is a typical hypomanic symptom, by the way!