Lincoln may be being overmodest here: although the book had already sold several thousand copies, none of the other readers seems to have discovered the message.
An overmodest beginner will make the mistake of playing only against her likewise beginning friends; the result is that she takes a discouragingly long time finding out how to use her racket properly and never gets a chance to return a really good serve.
Like many others 'clothed with a little brief authority' he was not overmodest in showing his importance.
Had Mac been overmodest, before, when he had said he was no great angler?
Just here I rise to remark: For effective purposes one must not be unduly sensitive or overmodest in writing autobiography -- for, being the events and memoirs of his life, written by himself, the ever-present pronoun "I" dances in such lively attendance and in such profusion on the pages that whatever pride he may have in the events they chronicle is somewhat abashed at its repetition.