特殊句型: never …… but ……
这个句型意为：“没有······不······”、“每当······ 总会·····”、“一······ 就会······”，　　或其他双重否定译法。
1）As a general rule, there is never a new theory but someone objects to it.　　(通常，一有新的理论提出就会有人反对。)
2）He never goes out but he drops in that bookstore.　　(他每次外出都会顺道去那家书店待一会儿。)
3）She never reads a book but she goes to sleep.　　(她一看书就想睡觉。)
● 这是一个表示双重否定的特殊句型。句型中的but 含否定意味。相当于without ……...。
先看个例句：My uncle never came to visit our family but he brought me some
presents.　　（我叔叔每次来我们家总会给我带一些礼物。）
　　这个句子可改成：　　My uncle never came to visit our family without bringing me some presents.　

楼主啥水平,
我一时竟然没看明白.

But as this repetition is not to be expected,但是由于这种重演是不可能的，
that which resembles most living one's life over again,那么最接近重演的
seems to be recall all the circumstances of it;似乎就是回忆了。。
and, to render this rememberance more durable,为了使回忆尽可能地保持久远
to record them in writing."就需要把它记下来。

为什么我看的版本是这样
Since such a repetition is not to be expected, the next thing most like living one’s life over again seems to be a recollection of that life, and to make that recollection as durable as possible by putting it down in writing.