Learn Russian: Моя душа в смятении.

Russian often treats intense emotional or psychological states metaphorically as physical spaces. Just like being in a room, when your soul is physically 'inside' a state of turmoil, you use в with the prepositional case to show location within that feeling.

Why does смятении end in -ии? Don't neuter nouns in the prepositional case usually end in -е?

Normally they do, but смятение is part of a special group. Neuter nouns that end in -ие in the nominative case (like здание or внимание) always take -ии in the prepositional case instead of the standard -е.

Is it common to attribute feelings to the soul (душа) rather than just saying 'I am in turmoil'?

Yes, very common. Russian relies heavily on the concept of the душа as the center of deep emotions and inner conflict. While you can translate this as 'I am in turmoil,' the Russian phrasing emphasizes a profound, core emotional state rather than a passing mood.

Could I just say Я в смятении instead?

Absolutely. Я в смятении is perfectly correct and frequently used for personal confusion or emotional disarray. Using моя душа simply elevates the tone, making it sound more dramatic, poetic, or deeply felt.