I taught an Effective Cycling (Bike Ed) class yesterday. Had trouble shifting in the rear all the way there. Stopped 3 times to adjust the barrel adjuster at the rear derailleur -- 1/4 turn CW, then 1/4 CCW, .
While demonstrating how the derailleurs work and explaining gearing and when to shift, the cable snapped at the shifter. Holy crap!! Naturally I didn't have a derailleur cable in my panniers (who does??) so got to do the road riding part of the class riding my beloved commuter as a single speed. Actually I had 3 speeds but found that the 52x12 and 42x12 made pulling away from a stop sign somewhat difficult -- and forget climbing. So did the entire ride in the 30x12 gear. Talk about some serious cross-chaining!
After the class I headed over to the bike shop. All Mike had was a Dura-Ace cable. I guess the new cable is now the best component on my commuter.
That's two tough lessons I've learned this week. 1. Check for tire wear every few months or 500 miles. 2. When the shifting gets weird it's time to replace the cables.

Seems life keeps me too busy to do the things I know I should do to the bike.