A Fibonacci retracement is only as useful as the swing it measures. If you drag the tool from a noisy internal high to a temporary low, the 38.2%, 50%, and 61.8% lines will look precise and still mean very little.
Start by naming the impulse you care about: the move that changed the short-term structure. On a daily chart that might be a multi-week advance; on an hourly chart it might be the last clean push into a session high. Ignore wiggles that did not attract a meaningful reaction.
Then ask whether both anchors are obvious to another trader looking at the same timeframe. If you need to zoom and squint to justify the high or low, choose a clearer pair. In class we practise discarding one “almost” swing before drawing anything.
Finally, leave the tool alone once price is mid-correction. Redrawing every few bars manufactures false confluence. Mark, plan, and wait for the reaction you actually wrote down.