Your summary of the lessons is especially valuable and is something that I've been thinking about for some time. Nobody is truly a lone wolf, and if they were, their quality of life would be very harsh and lonely.

Admittedly it feels a little strange to connect this lesson to this movie; when I think of surrounding myself with quality friends, preparing for a battle to the death against almost impossible odds isn't quite what springs to mind but it emphasizes the loyalty and comraderie among the 300, who fought and died valiantly and gloriously. But quality friends don't necessarily come for free, just as they say you are the sum of your closest friends, the same is true for them; they are the sum of their friends which can include you. So we ourselves still have to be dedicated to self improvement, and if they are too there's a positive feedback cycle where everyone as a sum keeps growing.

Your note that bravery simply means taking action is too true; many of my regrets are precisely because I didn't have the courage to just step up and do or say something. In retrospect, if I had just acted at that time then I'd be the richer for it (in experience, if not actual cash).

I guess a movie I'd be interested in having get analyzed is Get Out. That was a mildly haunting movie with some nasty twists... Unless you also can review Netflix series, in which case how about Black Mirror (but it'd have to be an episode at a time)?