A phrase in my smart review that i mess up constantly is
Sê simpático com os outros
(Be nice to others)
My brain keeps wanting to say sê simpático aos outros
I know Pt & En don’t map 1:1 with conjunctions, but why does “be nice” use “with” instead of “to” in this phrase?
Olá, @kenji! I don’t know if there is a satisfactory answer to that question. I’ll just add that it is also acceptable to phrase that sentence with “para” or even “para com”, and “para” is closer to the English “to”. I could just as well ask why “be nice” asks for “to” instead of another preposition, in English 
Thanks! I guess I didn’t mean so much “argh, why is it like this” but more “how do I know when to use ‘com’ in Pt for a phrase En would use ‘to’?”
Is it just memorizing which phrases use “com”, or is there a subtlety in the meaning that would make it easier to figure out how it works even for phrases I haven’t seen?
“Be nice to the others” is probably a shortening of “be nice towards the others”, and that’s a change that has happened relatively recently. I guess towards is a good mapping for para.
I can imagine saying “be nice with the others” and even “be nice for the others”.
One of the fun things about learning another language is it prompts the question: how well do I understand my own language?
@kenji, I would say that you’ll need to rely more on memorization here. It might help if you remember that the related verb simpatizar (to like; to sympathise…) also requires the preposition com.
@coljay, indeed. Along with that question, I often also ask myself how to explain the intricacies of my language 