When i was reading an entry about 暗峠 the writer mentioned an expression using 峠 which is「今夜が峠です」, they said that when a close person is seriously ill and are on their deathbed this expression is often used.
親しい人が重病で、生死の境目にある時、我々は比喩的に“今夜が峠だな。”とよく言います。
So what does it mean exactly?
Is it something like they are expressing how difficult a situation it is since 峠 has the meaning of difficult part or does it have the subtle meaning of wishing the ill person survives and expressing their sadness?
Are there any similar expressions in English?