Over looking castling but later over looking mate.
Have you ever had an attacking idea that only works if your opponent does absolutely nothing for about 3 to 5 moves and then you score a checkmate? That is exactly what happened to me when I played this game not long ago on lichess in a tournament.
At the very least, I learned that even though I am prone to over looking details, I know that my opponent might possibly over look them as well. So, never resign!