ignoring your opponent's threats!Here's a simple example:
Black went ahead with their plan to gobble the c-pawn:
Here's a not much more complicated example:
In both cases, the players who lost were more interested in what they were doing than their opponent's threats.
By the way, you may see from this how pointless it is to move a piece, and hold onto it while checking for problems. If you are holding onto it, you can hardly see the board anyway, but... the problem might not be with the piece in your hand, it's the piece you have undefended!