Shomer psaim Hashem

The entire concept is hard for me to understand. It's a nice thought that Hashem protects the fools but here (nidda 45a) there's a simple suggestion - let them be meshameshes b'moch and then we won't have to rely on Hashem protecting the fools. So why don't the Chachamim tell her to try to protect herself from danger but if someone is too stupid to listen then Hashem will protect her anyway?

Also, the Chachamim say "achas zu v'achas zu meshameshes k'darka." When I first read the gemara I assumed that it meant that they argued only in the case of ktana and said either way - whether she's less than 12 or over 12, she should be meshameshes k'darka because Hashem will protect the fools. However, I was corrected that they meant in all three cases - ktana, meuberes and meinika. Rashi and Tosafos don't clarify but that is the way Artscroll explained. I looked up a couple of other Rishonim/Acharonim this morning and didn't see anyone comment on it but it's clear that everyone understands the machlokes the way Artscroll explained it. The thing that bothers me about that pshat is that the "fool" here is the lady. So it makes sense to apply "shomer psaim Hashem" in the case of the ktana because she's acting foolishly but Hashem will protect her anyway. However, by a meuberes and meinika we're worried about the baby/fetus. The baby isn't acting foolishly. Yet we're telling the mother to be meshameshes k'darka because Hashem will protect the fools. We need Him to protect the baby not the mother here. Whatever, it's not such a strong question but it just bothered me because it seems that we're misapplying the passuk here.

As I said, I looked around a bit for an answer and didn't find anything but I did come across some other points on this meshameshes b'moch. It seems that it's a machlokes Rishonim how to understand this machlokes tannaim. Does R' Meir say that these three women have to be meshamshes b'moch and the Chachamim say that it's up to her (this pshat would help answer the first question) or does R' Meir say that these three women are allowed to but the Chachamim forbid it even in these three cases (that's how I understood it when I read the gemara).

None of this is halacha l'maaseh for a number of reasons. Suffice it to say that if you're wondering what to do for yourself that you should ask a shayla and not rely on this post (of course you should never rely on anything I say for halachic purposes).

For more on this topic you can see what Kollel Iyun Hadaf had to say on yevamos 12b.