> I don't know if I'll ever be able to master any language anymore

Even with just a handful of languages in my toolbox, I feel this way too. A mixture of unease and anxiety.

In addition to syntactic variations, I find that the notion of writing idiomatic code in a given language amounts to more thinking overhead which eats into productivity. I'd need to be programming in the same language over a long period of time for idiomatic code to come more naturally. Can't seem to just instantly switch like some talented folk out there.