My worst mistake was to not follow the commit process one time. I was multitasking a lot and forgot to run the tests for one of the commits I made. Next thing I know the whole Dev team started complaining that the Head of the branch was all messed up and blaming me. Long story short, it wasn't my change but I had to take the bullet and revert it for not following the process. It was deserved. Process is just as important as writing the code.