On May 14th, 2015 we merged one of my mistakes into Ninja Forms core. My mistake caused exactly zero fatal errors and zero customer support tickets. Actually, the code worked perfectly!
This is not something I would boast about, but it is a teachable moment.
My Simple Mistake
What did I do wrong? I broke a naming convention. While this did not create a single issue for anyone using Ninja Forms, it did create a maintenance headache for the rest of forever...
From now on, because of my simple mistake, we must always support this method for backwards compatibility. If someone somewhere, anyone anywhere, extended Ninja Forms and used my mistaken convention in their code, then removing that simple mistake would break their site.
It my time before developing Ninja Forms most of my work was distributed in a small controlled network. I had full access to every copy of my code. If I needed wanted to change something then I changed it, never thought twice about it, and left for the day.
However, Ninja Forms is currently installed on over 200,000+ websites. Every change that we make has a lasting effect.