As soon as I began, it seemed impossible to write fast enough - I wrote faster than I would write a letter - two thousand to three thousand words in a morning, and I cannot help it.

Jackson describes a burst of compelled productivity: once she starts, the work seems to outpace her ability to get it onto the page. The comparison to writing a letter emphasizes how unusually rapid and unselfconscious the flow feels—less like crafted literature than urgent communication. The specific tally of “two thousand to three thousand words in a morning” suggests both pride and astonishment, while “I cannot help it” frames the act as something driven by inner necessity rather than mere discipline. Read this way, the remark captures a familiar writerly experience: inspiration as pressure, and composition as an almost involuntary release.