So, this sentence doesn’t match what’s written on Tatoeba where the sentence is “Reg dich doch über so etwas nicht auf!” (N.B the Tatoeba sentence uses the imperative which is a closer match to the English original sentence). Also, the Tatoeba sentence doesn’t give any indication that it has been modified.
I note that the English sentence on Tatoeba is different as well (a minor difference in interpretation of aufregen meaning “excited” instead of “upset”).
What I would like to know however, is what does duch mean, and what is its purpose in this sentence?
Also, is the second so needed, as the English sentence doesn’t say “so upset” or something similar?
“doch” has many usages.
The core meaning of “doch” is an opposition, a contrast, something is not as expected.
You use “doch” when you feel that things are different from what they appear or what others think, and you would expect that it’s normal to see it the way you do, and you are surprised that others think differently.
Das Kleid ist gelb.
Das Kleid ist doch nicht gelb! Es ist doch grün! (How can you say it’s yellow, when it’s clearly green?)
Wo sind denn meine Schlüssel? Ich habe sie doch hier hingelegt?
(Now where have my keys gone? I did put them here, didn’t I?)
Here again it’s a case of surprise and unmet expectations. The keys are not where they had been put, and thus where you expect them to be.
In the sentence in question, it expresses the surprise of the speaker at the fact that someone got upset. Maybe the issue is too petty to be upset about, or maybe it’s a “what would the others think of you?” thing.
Now, the “so” is really not essential to the sentence, but it complements the “doch” and makes it more natural and idiomatic all around.
Thanks so much for your explanation. I’ll be sure to have a good read of the article you linked to, as these types of things (modal particles?) are something I see and tend to just accept rather than try to understand.
In this case though, I had already accepted the “doch” as one of those necessary-for-some-unknown-reason particles.
My question was about the “duch” i.e. the third word in the sentence.