Was dich nicht umbringt macht dich stärker Türkisch

Thank you, Hutschi. This is helpful. It is well-known that Nietzsche believed that we become 'heroes', as it were, by overcoming sometimes huge obstacles - even though the man himself was a rather dismal individual; poor, sick and lonely. His work is shot through with this idea. But that, of course, is not the point at issue here. If I am to quote and refer to him (and other philosophers) on the point of pain and suffering in life then I need to make sure I have his OWN words correctly translated. It is often translated in a number of different ways in English. Translating any complex or abstract idea from one language system to another is always going to be fraught with problems (actually, there is a whole branch of philosophy about that very subject - but we need not worry about that here).

I have seen this quotation in English as:-

'That which does not kill me makes me stronger.'And from what you say it does sound as if that is the best LITERAL translation.
I have also seen it variously translated as:

'That which does not destroy me makes me stronger.'
'Whatever does not kill me makes me stronger'.
'My strength comes from that which does not kill me'.
'What does not destroy me is what makes me stronger'.

And so on.
None of these, though, I see from what you say, are exactly literal translations. German is a very sophisticated language and it is as complex and as subtle as English. But it is clear that German expresses its subtle ideas often in different ways from English. That we would expect.
As I speak and write no German at all, I have to rely on those who do to assist me in trying to get the German subtleties - in this case, of what Nietzsche intended - into comparable subtleties in English. I hope that make sense?
So, do we need best of all a literal translation? I'm not sure.

However, what you say about hard work (and I think you mean REALLY hard work - comparable, perhaps to the fabled 'Labours of Hercules' in Greek mythology?) is helpful here. I am inclined from what I know of Nietzsche's teachings, to think that that is what he is getting at here. Like I said, he prefaces this axiom with the words 'From life's school of war'. I don't know what his actual words in GERMAN were here, but it is a strange idea, a strange piece of metaphor, is it not? And in any language I think this can only refer to what I, as an English speaker, would call 'hard won life experience'. Yes? Almost, perhaps, like a kind of 'wrestling match' with one's very soul (that is my own metaphor). Compare, for example, Hercules' encounter with the 'old man of the sea' ; how he had to hold onto him very tight indeed, even though he kept changing form in order to throw Hercules off.
English (or American English) speakers on this forum will know, I'm sure, the English idiom ' It nearly killed me' ... meaning it was immensely hard, taxing, draining, even 'soul destroying' but, as an American might say 'I kept hanging on in there'. Yes!!!
Thank you, Hutschi. You know, I think I just started telling you some of the ideas I need to put in my thesis on this point. Hmmm!!
Anyone else: if you have advice to share, please do.

PS: Yes, I take your point also about life as a battlefield (so to speak) and the mateahpor of war. Thank you.
Many thanks - edwardtheconfessor