Flustered to the point of incompetence. [adjective]

Have you ever been supervised so closely, nagged so incessantly, watched so
intently by a critic, spouse, or boss that your performance grew sloppier as
you went along? In English, you might say you were "flustered" or "jittery."
In Yiddish, you would say you were "farblonged." Neither of these words,
however, puts any blame on the unwanted supervisorial attention that brings
on this nervousness and disintegration of composure in the first place. The
German fisselig (rhymes with "thistle fish") conveys a temporary state of
inexactitude and sloppiness that is elicited by another person's nagging. It
is the precise answer to the unkind question "What the heck is wrong with
you today?"

Everyone has been in a classroom in which the teacher managed to intimidate
students into speechlessness, whether or not they knew the material. Spouses
trying to teach their mate how to drive an automobile often exhibit a streak
of this trait. Call these not-so-helpful advisers fisseligers. If someone
who has driven you over the edge of your ability to cope then asks you what
is wrong, reply, "I'm fisseliged." Your tormenter either will be stunned
into puzzled silence or else will feed you your straight line by asking,
"What is that supposed to mean?"

From They Have a Word for It: A Lighthearted Lexicon of Untranslatable Words
& Phrases Howard Rheingold (Sarabande Books, 2000)