It's all good character-building stuff and hopefully we learn from our mistakes.
But it's very easy to be heavy-handed with cutting nut slots, I over-cut all the time. Even with proper nut files, no file is the same in terms of cutting power, and if you've just been using one that took 10 strokes to file a small distance, you need to mentally reset before the next one as it might take just 2 strokes to do the same with the next file. So keep a constant vigil on visual heights and remember to look at the dust pile created (remembering that the wider slots are always going to create more dust than the thinner ones for the same slot depth).