For years I have been saying それが人生{じんせい} in Japanese to mean "such is life" / "c'est la vie". In fact English has a few other ways to express the same thing, and so do the other European languages I am familiar with.

Well my Japanese friends and acquaintances always understood, seemed to enjoy it, and never corrected me.

On my current trip to Japan I also learned 仕様{しよう}が無{な}い as having a similar meaning, perhaps literally more like "it can't be helped".

But only this morning for the first time have I been told that the first one is not actually a set phrase in Japanese, that it's merely the literal translation of the English (or French) phrase into Japanese.

So is it true that only 仕様が無い is used in idiomatic Japanese or is it just that the person who corrected me just isn't used to それが人生 even though other people in other parts of Japan, or people of other generations, might use it in their normal speech?

And what about other ways to express this sentiment? Since I originally asked this question people have added other variants in comments:

- 世の中はそんなもんだ
- 人生ってそんなもんだよ

Is one any more idiomatic, natural, Japanese-sounding? Is this a sentiment Japanese actually express at all?