My secret source of shame is that I'm a fairly poor bike mechanic. I cut my teeth at a bike co-op that I cofounded, which means that I was tinkering with junkers. It was the "hammer-and-duct-tape" school of bike repair.
Then I started riding fixed gear bikes. Fixed gear bikes are a small step above the hammer-and-duct-tape school of bike repair. It's very easy to wrench on fixed gears, and very hard to mess anything up. No finesse is required. No special tools are required. In fact, if you don't have a chainwhip for changing cogs, you can make do with your frame and the chain that's already on it.
I'm tenacious, though, so have thrown myself headfirst into a few challenging tasks. I've built a handful of wheels, and I also built up my roadbike from a bucket's worth of parts. I measured each length of cable and housing a dozen times before cutting it (I still need to re-trim since I changed stems and handlebars). I fiddled with the alignment and tension of each derailleur about a hundred times in the first week or two. Practice makes perfect, and I got a lot of chance to practice on this one bike. Not quite at perfection yet, but I'll attribute that to Ergo levers that need to new G-springs.
Casting shame on my clumsy hands is a mechanic in a bike shop in Bloomfield, New Jersey who is blind. Apparently the tasks that I muddle through can indeed be mastered through persistence and experience, but also can be done without sight.
I'd love to be a fly on the wall in that shop, seeing what tasks Mr. Tinsley does and doesn't do, and how. Does he measure lengths of chain? Does he feel the alignment of a stem to the front wheel?
I just read an interview with Roger Aspholm, a dominant local racer. He talks about experienced riders training by feel rather than by science: knowing what your body is capable of, how to push your limits, how your body responds to duress. It's neat to think that the love for the bike could lead to similar feel for tools and bikes, not just one's body.
Several years back, as a grimey mechanic was putting cranks onto my bike while I hung around asking questions about everything that I could, I asked him how he knew when the square-tapered cranks were on snug enough. He had just leaned into the wrench, bringing it and the crank together, smoothly and forcefully installing the crank onto the spindle. He shrugged and mumbled, "Been doing it for fifteen years."