Slavs in general tend to struggle with "a/an/the" in English, because most Slavic languages lack articles. Out of the entire language family, only Bulgarian uses definite articles.

Articles feel unnatural to me, too. I got used to them, but in a similar way that one gets used to a prosthetic arm: you can do things, but it feels mechanic and distant.

Just like the passive voice, then?

*mechanical