I have similar issues but with the coding part, usually my brain stops working for the time of an interview and then makes me hate myself for the rest of the we

I have similar issues but with the coding part, usually my brain stops working for the time of an interview and then makes me hate myself for the rest of the week. The only advice people gave me, that made sense, was: training. Go do all the possible questions you can find to the point you could do it in your sleep. For your issue, since it's open ended, it's not "as easy", but you can still read and think about as many of those questions you can find, open forum posts and debate what other people would have answered and why, to see better where your reasoning is lacking/failing something.