Now he would never write the things that he had saved to write until he knew enough to write them well. Well, he would not have to fail at trying to write them either. Maybe you could never write them, and that was why you put them off and delayed the starting. Well he would never know, now.
If a writer of prose knows enough about what he is writing about he may omit things that he knows and the reader, if the writer is writing truly enough, will have a feeling of those things as strongly as though the writer had stated them. The dignity of movement of an iceberg is due to only one-eighth of it being above water. A writer who omits things because he does not know them only makes hollow places in his writing.
If a writer stops observing he is finished. But he does not have to observe consciously nor think how it will be useful. Perhaps that would be true at the beginning. But later everything he sees goes into the great reserve of things he knows or has seen.