I wanted to tell you something, but I have lost my train of thought.
I lost my train of thought when there was a loud boom from the factory next door. It interrupted my flow of thinking.
I promise I'll tell you when I remember again—if I remember again—but for now, I've lost my train of thought.
He lost his train of thought in the middle of a word. This was somewhat usual for him—he was pretty scatter-brained and easily distracted.
It was quite the unfortunate circumstance when I lost my train of thought smack in the middle of an important presentation for my boss.
She lost her train of thought when she smelled the spicy scent of meat sizzling at the Mexican restaurant across the street. She was hungrier than she had thought.
The young girl lost her train of thought in a midst of a story, but she wasn't fazed—she just began telling a completely different story as if nothing had happened.
One of the most frustrating feelings is when I lose my train of thought in the midst of an important conversation. Why does my brain do that?
He was somewhat infamous for the times he had lost his train of thought in the middle of some exciting revelation. In the middle of revealing the meaning of life, he'd suddenly lost it and paused in silence, frustrated.
Cindy was funny when she lost her train of thought—she would become very nervous and rub her head, as if that would somehow get the thought back on track.