A few weeks ago, my back started hurting; I think it was because I'd recently switched to shoes with extremely thin soles (leather, maybe 2mm?) as opposed to merely very thin soles (rubber, 5mm), and walking with those shoes on concrete was too jarring. So I ordered another set of the less thin version, and wore sneakers in the meantime; and my back started to get better. (And my coworkers commented on my wearing sneakers; I wasn't expecting that.)

Now I'm back to the sort of shoes that I'd been wearing for a year and a half; but something isn't feeling right. Both in my back and in my walking: I think I'm overconscious about how I'm walking, and sometimes I'm having my heel hit first, sometimes I'm having the ball of my foot hit first, sometimes I'm doing some sort of weird halfway thing, and some subset of those leads to unexpectedly abrupt contact.

Hopefully this will sort itself out soon...