It's easy to get complacent with something you've probably done a hundred times. While I agree that's no excuse, the important things are your snake is okay, you learned a hard lesson, and identified an issue and a solution. It sucks making a mistake that could or does hurt an animal under your care I know, but personally I think you have a pretty good attitude getting some hard to hear, but honest feedback.
Good reminder for all of us that it only takes a few seconds of losing focus to make a mistake.