This was 8 years ago, so I just remember us being in some sort of merge pickle, my colleague going, "Ah, git is easy if you just understand it as..." and then jumping in to fix it. Which he'd done a few times before successfully, as he really did understand it well. But this time he did something wrong and data was lost.

He was very apologetic about it, and it wasn't more than a day or two of work, so I was ok with it. But it was one of many experiences that have left me permanently suspicious of doing anything fancy with git. Which is fine, because for a lot of reasons mostly not to do with any particular VCS, I work to keep branching to an absolute minimum.