I recently spent an exhausting day tracking down a memory leak problem. It wasn’t the hours and hours working out a recipe to reproduce the problem that finally got to me. It wasn’t finally realising that the problem was being caused by a third party library (not my fault!) that finally got to me.
You can be debugging and debugging for hours and hours, and you can be assured that it will be the smallest of trifles that finally sends you around the bend.
Like spending hours reproducing an OutOfMemoryError, then
remembering that you don’t get a stack trace with an OutOfMemoryError.