Sophie stood on the gravel path, thinking. She tried to think extra hard about being alive so as to forget that she would not be alive forever. But it was impossible. As soon as she concentrated on being alive now, the thought of dying also came into her mind. The same thing happened the other way around: only by conjuring up an intense feeling of one day being dead could she appreciate how terribly good it was to be alive. It was like two sides of a coin that she kept turning over and over. And the bigger and clearer one side of the coin became, the bigger and clearr the other side became too.

其中关键是这句：The same thing happened the other way around: only by conjuring up an intense feeling of one day being dead could she appreciate how terribly good it was to be alive.

这里的 could 搞不懂。

各位大侠显一下身手吧。

是表强调把,强调by的内容

是 倒装强调的意思吧。

那么是什么意思呢

In this sentece:

The same thing happened the other way around: only by conjuring up an intense feeling of one day being dead could she appreciate how terribly good it was to be alive.

only...could...   is  a fixed strcture.It means "只有...才...".