So today I checked in a changelist containing (what I thought were) relatively minor changes to 40 files.
Turns out I had switched two parameters in a function call (so what should have been call(String a, String b) instead was call(String b, String a). If I had run *any* test at all, I would have caught it. But I didn’t, assuming that the changes were simple enough (and I had had someone else look over the code with me and it looked fine to both of us). Result: everything broke, hard.
Took me about 30 minutes to get things back in a happy state (fixing up 40 separate files) and then another 3 hours or so to properly revert out everything.
It was an incredibly dumb thing of me to do (submit any change, even a seemingly minor and trivial one, without testing first).

Also, I managed to rip the green shirt I really like.

I’m so upset with myself :-\