An idea you don’t write down has the lifespan of a sneeze.

Thoughts feel permanent while you are having them, which is why nobody reaches for a pen. Memory holds gist rather than detail, so the specific version with the good phrasing dissolves in minutes and leaves only the sense that you had something. The loss is invisible, which is why it keeps happening.

Keep one place, a note on your phone or a paper in your pocket, and put things there unfiltered and badly written. Do not judge at capture time, judge later. Most people find their good ideas were not rarer than they thought, only unrecorded.