> There's nothing like fixing a stupid but critical bug in old crappy code that is so bad you can't imagine how anyone wrote such garbage and considers themselves a professional.. and then realizing you were the one that wrote it. That's a nice wake-up call.

Alternatively there's nothing like having a junior colleague investigating a defect in code you once wrote ask you what it does and then have to publicly declare that that it was crappy garbage that you can no longer decipher.