I don't remember much of the Arabic I learned, but I mastered the script because I found writing English-in-Arabic-script so much easier as a lefty that I wrote a lot of my notes that way.
This comes up when I practice calligraphy as well. I'm right handed and if I'm doing an LTR script (like English), I can manage fairly well without a guard sheet but if I'm doing something like Arabic, I need to be way more careful since my hand will be on top the fresh letters I write. That, apart from the lack of good instructional material, is probably why I moved away from Arabic calligraphy although I really love the form of it.
Medieval Arabic scribes would turn the paper on its side and write from top to bottom to avoid exactly this problem. It's why Arabic numerals are sideways compared to European "Arabic" numerals.