Have you ever reached to take off your hat, only to find you’d removed it earlier? Or, more poignantly, ever reached for the phone to dial a friend with a special story, then remember she had died a year ago?
This one’s easy to say, and actually not all that hard to do.
Just observe one of your angers or expectations or terrors until it "thins"; that is, until it stands out as only a mental event among others. In other words: Study it to death.