I guess this isn’t exactly the same thing as in その時はその時で, but I just thought I’d offer a simple phrase that I think I’ve heard a few times in anime that might make the essence of the 〜は〜で easier to remember:「君は君でいいよ」(and similar sentences) are used to mean ‘you’re fine the way you are’ and offer reassurance. (OK, actually, I still think these two phrases work more or less the same way, but that’s probably just got to do with how I personally see で.)
あらう(であろう)の意味 - goo国語辞書
あらう(であろう)とは。意味や解説、類語。[連語]《連語「である」+推量の助動詞「う」》だろう。「明日はよい天気―◦う」「不正がまかり通る世の中でよいの―◦うか」[補説]話し言葉では、ふつう「だろう」を使う。 - goo国語辞書は30万4千件語以上を収録。政治・経済・医学・ITなど、最新用語の追加も定期的に行っています。

Not sure about that though.
