I've avoided C++ for most of my career, but one idiotic mistake I do remember making was accidentally leaving an open curlybrace at the end of one of my source files. The C++ compiler ran and reported 1000s of compilation errors all through every single other file -- in my code, throughout all the library code I included.

Easily diagnosed if you're working incrementally, one small change at a time, and making checkpoints with version control: `git diff`, carefully review the diff of what you changed since the last checkpoint where things were more or less working. I must have not been disciplined enough to work like that at the time.

Troubleshooting systems integration failures is also character building for getting better at diagnosis from errors. Sure, it's failing, but let's try to figure out the immediate layer of failure from the logs, error messages, symptoms: name resolution? tcp? tls? http proxy? authentication? authorisation? api spec misalignment? error in our application code or the system we're directly talking to? unexpected data? error in some other system that we depend upon transitively? each time you hit a new novel failure mode, or fail at one level deeper, you're making progress!