One. I was typing in a terminal window and viewing the results of my work in a browser window. I couldn't see any changes from what I was doing. A common rookie mistake is to type into one environment and look for results in a different environment, such as working on the development server and checking the production server. I'm no rookie so I have safeguards against this, like naming things "dev" and "production". And just to be certain, I made a huge, deliberate error that would have broken things, and sure enough, I could see in the terminal window that things broke, so I could be completely sure that I wasn't typing on one server and viewing on a different server. Do you see what just happened in that last sentence? It took me about an hour to catch on.
Two. I have a function that I have strongly suspected for a very long time should be recursive. I just allowed it to be recursive. It works better. I feel relieved.
Three. That function that's now recursive? It just broke again.