The speaker seems to be looking back at a time that involved a child, "you a child still," and at himself in a very different, grimmer place: "in an office / pickled in wine and rage." The title, "Making history," works in two ways. It suggests the speaker is revising the story, and it also hints that this ordinary, unhappy stretch of life is the history actually being made.
The first lines say that reading is done "for memory's sake," yet what's being read is "a history of the present." Past and present blur together. The line "I make changes to it" feels like an admission: the speaker edits, softens or reshapes what happened, perhaps to cope.
The mood is quiet but bitter. The image of being "pickled" is vivid and a little darkly funny, as if the speaker has been preserved in his own anger and drink. Set against the child's innocence, it leaves a sense of regret and distance.