Another related word is "agony", which originally referred to mental struggle.

Huck was silent for some time, engaged in a mental struggle.

A mental struggle, fighting all the way, sheer exhaustion threatening to swamp him.

Despite his mental struggle with pronunciation, something in the beauty of the language thrilled him.

It's been a little bit of a mental struggle.

Swofford's narrative focuses on the physical and mental struggles of the young troops.

It still took quite a mental struggle before Falconer answered her.

Her resulting original script explores both physical and mental struggles of being lost at sea.

After a lengthy mental struggle he came to the conclusion that he was in a hospital.

In the days which followed, another mental struggle was taking place in the Remington family.