Yeah! Absolutely yeah!
I once, very long ago, had an idea for a story that was absolutely brilliant. Incandescent, even. So I dutifully typed up the intro section and yawned and told myself that I'd surely remember the main theme when I got up the next morning.
When I woke up, that brilliant theme was gone. Even when I reread what I'd typed, it was gone, vanished like the morning dew in a desert. I still have that fragment. It still taunts me, heckles me, thumbs its nose at me when I read it.
All because I was "too tired" to summarize the main theme.
Another masterpiece lost to posterity.