The speaker stands in front of a mirror and can't decide what to believe. One moment she seems to see a body that is "pretty" and a real loss of weight; the next she suspects the mirror is tricking her. That doubt doesn't lead her to stop, though. It leads her to the opposite conclusion: "its only a few more kilos."
What stands out is how casually she talks about something dangerous. Fasting and drinking water are tossed off as "a bit" here and there, as if this were a minor errand. She calls it a "journey" and promises it's "a short one," but the promise to stop keeps moving further away. The lowercase writing and missing apostrophes make it sound like a passing thought or a private message, which makes it feel more intimate and more unsettling.
The mood is calm on the surface and anxious underneath. The speaker sounds sure of herself, but her reassurances read like a way of persuading herself that she is in control, and the poem suggests she may not be.