Is the sense of control we get from a perfectly adjusted rear derailleur more a result of the mechanical precision itself, or is it largely psychological - a confidence booster that comes from knowing our bike is dialed in, allowing us to push ourselves harder and ride more efficiently? Does the feeling of control actually translate to improved performance, or is it just a placebo effect that wears off once we hit the wall of physical fatigue or technical challenges? Can we really attribute improved shifting performance to the derailleur adjustment alone, or are other factors like chainring wear, cassette condition, and cable tension playing a much bigger role in the overall shifting experience?