"One Little Word Shall Fell Him"

At first, I thought the Poetry Foundation wrong when it put the line in "I must down to the seas again" in Masefield's "Sea Fever" ("go" was missing).  So, I started reading around and found that those lines originally had "go," but he removed them 20 years later.  Then, 20 years later again, he replaced them.  Finally, he said he just wasn't sure which to do.  That's quite a bit of deliberation!