A grumpy regular at my bike co-op told me I was adjusting derailleurs wrong, and it rewired my brain
He watched me turn the barrel adjuster a quarter turn and told me to stop guessing and actually shift through all 11 gears on the stand first, every single time. Now I spend the extra 30 seconds riding through the cassette on the repair stand before it ever touches the ground, and my comeback rate on tune-ups has basically dropped to zero. Anyone else got a check they do on every single bike no matter how simple the job looks?