No, please, I fully support this thread is venturing into the philosophical. I've been burning out on the "Bicycle Mechanics" subforum lately, I feel like I've been handing out too many fish and not helping to teach the art of fishing.

I taught myself how to fix bicycles, this was before the internet, so it was mostly trial and error. I made a lot of errors, but I also took the time to really notice how things work, and to deconstruct some of the engineering decisions made to design the parts. The biggest head start you can give yourself now that we're in the internet era is to familiarize yourself with the names of parts, once you have those, you can google any problem you may have.

The thing you [one] need[s] to remeber above all else is that it's a machine- it's logical, if it doesn't work one day, something is broken. Machines don't have moods; machines either work or they don't. That's not to say problems can't be intermittent, but it is to say that if it malfunctions once, it will continue to malfunction.

Quick thoughts:
Bowden cables are based on tension- one direction is a human input and the other direction is spring energy stored from the human input. Basically, if you remember that you can't push a rope, you'll be lightyears ahead of the game when it comes to cabled systems. Similarly, every one bearing has a matching bearing on the other end of the axle.

The key to understanding a bicycle is being able to see the complete bicycle instead as a grouping of distinct component (AHA!) systems (suddenly the "integrated" nomenclature of the STI brifter comes into focus as well)- the brakes are each a distinct system, the derailleurs have a little interplay, but are mostly distinct, the bearings are a system, the wheels are a system of static tension, the tires are a system of pneumatic pressure. If you can break it down, you'll be amazed how easily traversed the landscape of bicycle maintenance is. Also, you'll be amazed how much the insight you have for other machines you've gained simply by learning how bicycles work.

Read Pirsig's Zen and the art..., but only the first half- once he starts crapping himself, it's a waste of time.

Just a heads up- There is a point when the knowledge of how things work won't be enough. There have been so many analogous, but distinct and incompatible products in the history of bicycles (threadings, tapers ISO/Metric) that there will come a time that you need to catch up on your history and educate yourself to the universe of parts. To do this, you can go take two routes- become a cat-lady style bike hoarder who buys anything novel that you come across and learn through experiential learning and reverse engineering, or you can start lurking a resource like the C&V forum and learning conceptually. Personally, I've taken a path where both routes are relevant in my life and both have been very helpful to me. If you don't have the resources to buy a pile of bikes [and flip them], then the aforementioned community bike shop is a perfect venue to work on offbeat parts and make some serious headway.