The writing process is very much like a nuclear chain reaction. In a nuclear reaction, uranium or plutonium atoms produce energy and release neutrons when they split in two (or fission) — those neutrons in turn collide with the nuclei of other uranium or plutonium atoms, causing those atoms to split … and if the fuel is arranged in sufficient concentration, the reaction will continue indefinitely (depending on some other factors) … it is, in other words, self-sustaining.
Writing is the same way, only the fuel isn’t atoms, it’s ideas. To create a self-sustaining “reaction” — or writing process — the enrichment level of pure ideas needs to be high enough so that one idea collides with the next and so on to sustain the reaction. Writing is, in other words, a thinking exercise, and a creative one. So when the process stalls, the solution isn’t to write, it’s to read … to promptly restart the reaction by inserting densely concentrated ideas from the richest possible sources: the classics.